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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2015	Apr. 24, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	ATRC
Entity Registrant Name	AtriCure, Inc.
Entity Central Index Key	0001323885
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		28,370,298

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 23,559	$ 28,384
Short-term investments	32,174	31,265
Accounts receivable, less allowance for doubtful accounts of $162 and $68, respectively	19,786	17,558
Inventories	15,106	14,257
Other current assets	2,790	2,044
Total current assets	93,415	93,508
Property and equipment, net	13,874	11,552
Long-term investments	2,025	8,894
Intangible assets, net	8,575	8,878
Goodwill	35,386	35,386
Other noncurrent assets	131	186
Total Assets	153,406	158,404
Current liabilities:
Accounts payable	9,659	7,621
Accrued liabilities	8,974	14,041
Other current liabilities and current maturities of capital leases	5,996	3,981
Total current liabilities	24,629	25,643
Capital leases	79	74
Other noncurrent liabilities	139	149
Total Liabilities	24,847	25,866
Commitments and contingencies (Note 7)
Stockholders' Equity:
Common stock, $0.001 par value, 90,000 shares authorized and 28,363 and 27,580 issued and outstanding, respectively	28	28
Additional paid-in capital	273,019	271,282
Accumulated other comprehensive loss	(798)	(348)
Accumulated deficit	(143,690)	(138,424)
Total Stockholders' Equity	128,559	132,538
Total Liabilities and Stockholders' Equity	$ 153,406	$ 158,404

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 162	$ 68
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	28,363,000	27,580,000
Common stock, shares outstanding	28,363,000	27,580,000

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$ 29,886	$ 24,847
Cost of revenue	8,151	7,190
Gross profit	21,735	17,657
Operating expenses:
Research and development expenses	5,609	4,001
Selling, general and administrative expenses	21,270	21,581
Total operating expenses	26,879	25,582
Loss from operations	(5,144)	(7,925)
Other income (expense):
Interest expense	(18)	(237)
Interest income	43	14
Other	(141)	466
Loss before income tax expense	(5,260)	(7,682)
Income tax expense	6	27
Net loss	$ (5,266)	$ (7,709)
Basic and diluted net loss per share	$ (0.19)	$ (0.31)
Weighted average shares outstanding-basic and diluted	27,069	24,766
Comprehensive loss:
Unrealized gains (losses) on investments	$ 37	$ (2)
Foreign currency translation adjustment	(487)	2
Other comprehensive loss	(450)
Net loss	(5,266)	(7,709)
Comprehensive loss	$ (5,716)	$ (7,709)

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (5,266)	$ (7,709)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	1,724	2,142
Depreciation	1,008	730
Amortization of intangible assets	303	355
Amortization of deferred financing costs	16	59
Loss on disposal of property and equipment	57	14
Realized loss from foreign exchange on intercompany transactions	251
Amortization/accretion on investments	184	83
Change in allowance for doubtful accounts	100	(17)
Other		95
Changes in operating assets and liabilities:
Accounts receivable	(2,685)	(1,045)
Inventories	(1,104)	(862)
Other current assets	(779)	312
Accounts payable	2,124	(531)
Accrued liabilities	(4,931)	(7,969)
Other noncurrent assets and liabilities	28	(55)
Net cash used in operating activities	(8,970)	(14,398)
Cash flows from investing activities:
Purchases of available-for-sale securities	(6,086)
Sales and maturities of available-for-sale securities	11,899	8,434
Purchases of property and equipment	(1,434)	(1,020)
Increases in property under build-to-suit obligation	(1,822)
Net cash provided by investing activities	2,557	7,414
Cash flows from financing activities:
Proceeds from sale of stock, net of offering costs of $0 and $215, respectively		65,872
Payments on debt and capital leases	(14)	(6,343)
Increases in build-to-suit obligation	1,822
Payment of debt fees and premium on retirement of debt		(100)
Proceeds from stock option exercises	516	1,395
Shares repurchased for payment of taxes on stock awards	(503)	(88)
Net cash provided by financing activities	1,821	60,736
Effect of exchange rate changes on cash and cash equivalents	(233)	(5)
Net (decrease) increase in cash and cash equivalents	(4,825)	53,747
Cash and cash equivalents-beginning of period	28,384	14,892
Cash and cash equivalents-end of period	23,559	68,639
Supplemental cash flow information:
Cash paid for interest	2	102
Cash paid for taxes		146
Non-cash investing and financing activities:
Accrued purchases of property and equipment	751	$ 124
Assets acquired through capital lease	$ 36

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Cash Flows [Abstract]
Offering cost for sale of stock	$ 0	$ 215

Description of Business and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2015

Accounting Policies [Abstract]

Description of Business and Summary of Significant Accounting Policies

1. DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Nature of the Business—AtriCure, Inc. was incorporated in the State of Delaware on October 31, 2000. The “Company” or “AtriCure” consists of AtriCure, Inc. and its wholly-owned subsidiaries. The Company is an innovator in surgical treatments for atrial fibrillation (Afib) and left atrial appendage management (LAAM). The Company sells its products to medical centers globally through a direct sales force and distributors.

Basis of Presentation—The accompanying interim financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (SEC). The accompanying interim financial statements are unaudited, but in the opinion of the Company’s management, contain all of the normal, recurring adjustments considered necessary to present fairly the financial position, results of operations and cash flows for the periods presented in conformity with accounting principles generally accepted in the United States of America (GAAP) applicable to interim periods. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been omitted or condensed. The Company believes the disclosures herein are adequate to make the information presented not misleading. Results of operations are not necessarily indicative of the results expected for the full fiscal year or for any future period.

The accompanying Condensed Consolidated Financial Statements should be read in conjunction with the audited financial statements of the Company included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 filed with the SEC.

Principles of Consolidation—The Condensed Consolidated Financial Statements include the accounts of the Company, AtriCure, LLC, the Company’s wholly-owned subsidiary organized in the State of Delaware, Endoscopic Technologies, LLC, the Company’s wholly-owned subsidiary organized in the State of Delaware, and AtriCure Europe B.V. (AtriCure Europe), the Company’s wholly-owned subsidiary incorporated in the Netherlands. All intercompany accounts and transactions have been eliminated in consolidation.

Cash and Cash Equivalents—The Company considers highly liquid investments with maturities of three months or less at the date of acquisition as cash equivalents.

Investments—The Company places its investments primarily in U.S. Government agencies and securities, corporate bonds and commercial paper. The Company classifies all investments as available-for-sale. Investments with maturities of less than one year are classified as short-term investments. Investments are recorded at fair value, with unrealized gains and losses recorded as accumulated other comprehensive income (loss). The Company recognizes gains and losses when these securities are sold using the specific identification method and includes them in interest income or expense in the Condensed Consolidated Statements of Operations and Comprehensive Loss.

Revenue Recognition—The Company accounts for revenue in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 605, “Revenue Recognition” (ASC 605). The Company recognizes revenue when all of the following criteria are met: (i) there is persuasive evidence that an arrangement exists; (ii) delivery of the products and/or services has occurred; (iii) the selling price is fixed or determinable; and (iv) collectability is reasonably assured.

Pursuant to the Company’s standard terms of sale, revenue is recognized when title to the goods and risk of loss transfers to customers and there are no remaining obligations that will affect the customers’ final acceptance of the sale. Generally, the Company’s standard terms of sale define the transfer of title and risk of loss to occur upon shipment to the respective customer. The Company generally does not maintain any post-shipping obligations to the recipients of the products. No installation, calibration or testing of this equipment is performed by the Company subsequent to shipment to the customer in order to render it operational.

Revenue includes shipping and handling revenue of $247 and $227 for the three months ended March 31, 2015 and 2014, respectively. Cost of freight for shipments made to customers is included in cost of revenue. Sales and other value-added taxes collected from customers and remitted to governmental authorities are excluded from revenue. The Company sells its products primarily through a direct sales force, with certain international markets sold through distributors. Terms of sale are generally consistent for both end-users and distributors except that payment terms are generally net 30 days for end-users and net 60 days for distributors.

Sales Returns and Allowances—The Company maintains a provision for sales returns and allowances to account for potential returns of defective or damaged products, products shipped in error and invoice adjustments. The Company estimates such provision quarterly based primarily on a specific identification basis, in addition to estimating a general reserve. Increases to the provision result in a reduction of revenue. The provision is included in accrued liabilities in the Condensed Consolidated Balance Sheets.

Allowance for Doubtful Accounts Receivable—The Company evaluates the collectability of accounts receivable in order to determine the appropriate reserve for doubtful accounts. In determining the amount of the reserve, the Company considers aging of account balances, historical credit losses, customer-specific information and other relevant factors. An increase to the allowance for doubtful accounts results in a corresponding increase in expense. The Company reviews accounts receivable and adjusts the allowance based on current circumstances and charges off uncollectible receivables against the allowance when all attempts to collect the receivable have failed. The Company’s history of write-offs against the allowance has not been significant.

Inventories—Inventories are stated at the lower of cost or market using approximate costs based on the first-in, first-out cost method (FIFO) and consist of raw materials, work in process and finished goods. The Company’s industry is characterized by rapid product development and frequent new product introductions. Uncertain timing of product approvals, variability in product launch strategies and variation in product utilization all impact excess and obsolete inventory. An inventory reserve based on product usage is estimated and recorded quarterly for excess, slow moving and obsolete inventory, as well as inventory with a carrying value in excess of its net realizable value. Write-offs are recorded when a product is destroyed. The Company’s history of write-offs against the reserve has not been significant.

Inventories consist of the following:


	March 31, 2015		December 31, 2014
Raw materials	$	4,484	$	4,429
Work in process		1,169		1,397
Finished goods		9,453		8,431

Inventories	$	15,106	$	14,257

Property and Equipment—Property and equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method of depreciation for financial reporting purposes and applied over the estimated useful lives of the assets. The estimated useful life by major asset category is the following: generators and other capital equipment, machinery, equipment and vehicles is three to seven years, computer and other office equipment is three years, furniture and fixtures is three to seven years and leasehold improvements and equipment leased under a capital lease are the shorter of their useful life or remaining lease term. The Company reassesses the useful lives of property and equipment annually, and assets are retired if they are no longer being used. Maintenance and repair costs are expensed as incurred.

Generators and other capital equipment (such as the Company’s switchbox units and cryosurgical consoles) are loaned at no cost to direct customers that use the Company’s disposable products. Depreciation of such assets is included in cost of revenue. The estimated useful lives of this equipment are based on anticipated usage by customers and the timing and impact of expected new technology rollouts by the Company. To the extent the Company experiences changes in the usage of this equipment or introduces new technologies, the estimated useful lives of this equipment may change in a future period. Depreciation related to these generators was $620 and $461 for the three months ended March 31, 2015 and 2014, respectively. As of March 31, 2015 and December 31, 2014, the net carrying amount of loaned equipment included in net property and equipment in the Condensed Consolidated Balance Sheets was $4,123 and $4,141, respectively.

The Company reviews property and equipment for impairment using its best estimates based on reasonable and supportable assumptions and projections.

Intangible Assets—Intangible assets with determinable useful lives are amortized on a straight-line basis over the estimated periods benefited. The Company reviews intangible assets for impairment using its best estimates based on reasonable and supportable assumptions and projections.

Goodwill—Goodwill represents the excess of purchase price over the fair value of the net assets acquired in business combinations. The Company tests goodwill for impairment annually on November 30, or more often if impairment indicators are present. The Company’s goodwill is accounted for in a single reporting unit representing the Company as a whole.

Other Current Liabilities and Current Maturities of Capital Leases—Other current liabilities consist of a financing obligation related to the construction of the Company’s new headquarters (see Note 7—Commitments and Contingencies). Current maturities of capital leases consist of capital lease obligations with maturities of less than one year (see Note 6—Indebtedness).

Other Income—Other income consists primarily of foreign currency transaction gains and losses, grant income and non-employee option gains and losses related to the fair market value change for fully vested options outstanding for consultants which are accounted for as free-standing derivatives.

The Company recorded net foreign currency transaction (losses) gains of ($163) and $5 for the three months ended March 31, 2015 and 2014, respectively, primarily in connection with settlements of its intercompany balance with AtriCure Europe.

The Company periodically is awarded grants to support research and development activities or education activities. The Company recognizes grant income when the funds are earned. The Company recorded grant income of $35 and $363 during the three months ended March 31, 2015 and 2014, respectively.

The Company historically issued stock options to non-employee consultants as a form of compensation for services provided to the Company. Because the non-employee options require settlement by the Company’s delivery of registered shares and because the tax withholding provisions in the awards allow the options to be partially net-cash settled, these options, when vested, are no longer eligible for equity classification and are, thus, subsequently accounted for as derivative liabilities under FASB ASC 815, “Derivatives and Hedging” (ASC 815) until the awards are ultimately either exercised or forfeited. Accordingly, the vested non-employee options are classified as liabilities and remeasured at fair value through earnings at each reporting period. During the three months ended March 31, 2015 and 2014, $13 and ($98), respectively, of expense (income) was recorded as a result of the remeasurement of the fair value of these fully vested stock options.

Taxes—Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rates is recognized in the period that includes the enactment date.

The Company’s estimate of the valuation allowance for deferred tax assets requires it to make significant estimates and judgments about its future operating results. Deferred tax assets are reduced by valuation allowances if, based on the consideration of all available evidence, it is more-likely-than-not that some portion of the deferred tax asset will not be realized. Significant weight is given to evidence that can be objectively verified. The Company evaluates deferred tax assets on a quarterly basis to determine if valuation allowances are required by considering all available evidence. Deferred tax assets are realized by having sufficient future taxable income to allow the related tax benefits to reduce taxes otherwise payable. The sources of taxable income that may be available to realize the benefit of deferred tax assets are future reversals of existing taxable temporary differences, future taxable income, exclusive of reversing temporary differences and carryforwards, taxable income in carry-back years and tax planning strategies that are both prudent and feasible. In evaluating whether to record a valuation allowance, the applicable accounting standards deem that the existence of cumulative losses in recent years is a significant piece of objectively verifiable negative evidence that must be overcome by objectively verifiable positive evidence to avoid the need to record a valuation allowance. The Company has recorded a full valuation allowance against its net deferred tax assets as it is more-likely-than-not that the benefit of the deferred tax assets will not be recognized in future periods.

A provision of The Patient Protection and Affordable Care Act enacted in 2010, as amended (Affordable Care Act), requires manufacturers of medical devices to pay an excise tax on all U.S. medical device sales. The Company’s expense related to the medical device excise tax, which was recorded in cost of revenue, was $155 and $114 for the three months ended March 31, 2015 and 2014, respectively.

Net Loss Per Share—Basic and diluted net loss per share is computed in accordance with FASB ASC 260, “Earnings Per Share” (ASC 260) by dividing the net loss by the weighted average number of common shares outstanding during the period. Since the Company has experienced net losses for all periods presented, net loss per share excludes the effect of 4,320 and 3,762 options and restricted stock shares as of March 31, 2015 and 2014, respectively, because they are anti-dilutive. Therefore the number of shares calculated for basic net loss per share is also used for the diluted net loss per share calculation.

Comprehensive Loss and Accumulated Other Comprehensive Loss—In addition to net losses, the comprehensive loss includes foreign currency translation adjustments and unrealized gains and losses on investments.

Accumulated other comprehensive income (loss) consisted of the following:


	Three Months Ended March 31,
	2015			2014
Total accumulated other comprehensive loss at beginning of period	$	(348	)	$	(139	)

Unrealized Loss on Investments
Balance at beginning of period	$	(54	)	$	(6	)
Other comprehensive income (loss) before reclassifications		37			(2	)
Amounts reclassified from accumulated other comprehensive income (loss) to other income		—			—

Balance at end of period	$	(17	)	$	(8	)


Foreign Currency Translation Adjustment
Balance at beginning of period	$	(294	)	$	(133	)
Other comprehensive loss before reclassifications		(324	)		(3	)
Amounts reclassified from accumulated other comprehensive loss to other income (expense)		(163	)		5

Balance at end of period	$	(781	)	$	(131	)


Total accumulated other comprehensive loss at end of period	$	(798	)	$	(139	)

Research and Development—Research and development costs are expensed as incurred. These costs include compensation and other internal and external costs associated with the development and research related to new and existing products or concepts, preclinical studies, clinical trials, healthcare compliance and regulatory affairs.

Advertising Costs—The Company expenses advertising costs as incurred. Advertising costs were not significant during the three months ended March 31, 2015 and 2014.

Share-Based Compensation—The Company follows FASB ASC 718, “Compensation-Stock Compensation” (ASC 718) to record share-based compensation for all employee share-based payment awards, including stock options, restricted stock, performance shares and stock purchases related to an employee stock purchase plan, based on estimated fair values. The Company’s share-based compensation expense recognized under ASC 718 for the three months ended March 31, 2015 and 2014 was $1,724 and $2,142, respectively, on a before and after tax basis.

FASB ASC 718 requires companies to estimate the fair value of share-based payment awards on the date of grant using an option-pricing model. The value of the portion of the award that is ultimately expected to vest is recognized as expense over the requisite service periods in the Company’s Condensed Consolidated Statement of Operations and Comprehensive Loss. The expense has been reduced for estimated forfeitures. FASB ASC 718 requires forfeitures to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

The Company estimates the fair value of time-based options on the date of grant using the Black-Scholes option-pricing model (Black-Scholes model). The Company’s determination of fair value of share-based payment awards on the date of grant using an option-pricing model is affected by the Company’s stock price, as well as assumptions regarding a number of subjective variables. These variables include, but are not limited to, the Company’s expected stock price volatility over the term of the awards and actual and projected employee stock option exercise behaviors. The fair value of market-based performance option grants is estimated at the date of grant using a Monte-Carlo simulation. The value of the portion of the award that is ultimately expected to vest is recognized as expense over the requisite service periods in the Condensed Consolidated Statements of Operations and Comprehensive Loss.

The Company estimates the fair value of restricted stock based upon the grant date closing market price of the Company’s common stock. The Company’s determination of fair value is affected by the Company’s stock price as well as assumptions regarding the number of shares expected to be granted.

The Company also has an employee stock purchase plan (ESPP or the Plan) which is available to all eligible employees as defined by the Plan. Under the ESPP, shares of the Company’s common stock may be purchased at a discount. The Company estimates the number of shares to be purchased under the Plan and records compensation expense based upon the fair value of the stock at the beginning of the purchase period using the Black-Scholes model.

Use of Estimates—The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expense during the reporting period. Actual results could differ from those estimates.

Fair Value Disclosures—The Company classifies and records cash and investments in U.S. government agencies and securities as Level 1 within the fair value hierarchy. Accounts receivable, short-term other assets, accounts payable and accrued liabilities are also classified as Level 1. The carrying amounts of these assets and liabilities approximate their fair value due to their relatively short-term nature. Cash equivalents and investments in commercial paper are classified as Level 2 within the fair value hierarchy (see Note 3—Fair Value for further information). Significant unobservable inputs with respect to the fair value measurement of the Level 3 non-employee stock options are developed using Company data. When an input is changed, the Black-Scholes model is updated and the results are analyzed for reasonableness.

Recent Accounting Pronouncements	3 Months Ended
Recent Accounting Pronouncements	Mar. 31, 2015
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	2. RECENT ACCOUNTING PRONOUNCEMENTS In May 2014 the FASB issued a final standard on revenue from contracts with customers. The standard, issued as FASB ASU 2014-09, “Revenue from Contracts with Customers” (ASU 2014-09), outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. In April 2015 the FASB tentatively decided to defer the effective date of ASU 2014-09 for entities reporting under U.S. GAAP from interim and annual reporting periods beginning after December 15, 2016 to interim and annual reporting periods beginning after December 15, 2017. The FASB also tentatively decided to permit entities to early adopt the standard. A full retrospective or modified retrospective approach may be taken to adopt the guidance in the ASU. The Company is evaluating the impact of the provisions of ASU 2014-09 on its consolidated financial position, results of operations and related disclosures.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6510796

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22583-107794

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22580-107794

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.10-01.(b)(6))
-URI http://asc.fasb.org/extlink&oid=27015980&loc=d3e46468-122699

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accounting Change
-URI http://asc.fasb.org/extlink&oid=6503790

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22499-107794

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=6372559&loc=d3e765-108305

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6372559&loc=d3e725-108305

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 01
-Paragraph b
-Subparagraph 6
-Article 10

+ Details

Fair Value

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value

3. FAIR VALUE

FASB ASC 820, “Fair Value Measurements and Disclosures” (ASC 820) defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value which are the following:

•

Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. An active market for the asset or liability is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. The valuation under this approach does not entail a significant degree of judgment.

•

Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The valuation technique for the Company’s Level 2 assets is based on quoted market prices for similar assets from observable pricing sources at the reporting date.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Unobservable inputs shall be used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date. The fair value of the Company’s Level 3 instruments are estimated on the grant date using the Black-Scholes model and they are revalued at the end of each reporting period using the Black-Scholes model. The fair value of the Company’s Level 3 contingent consideration was estimated on the acquisition date of Endoscopic Technologies, Inc. and was revalued at the end of each subsequent reporting period.

In accordance with ASC 820, the following table represents the Company’s fair value hierarchy for its financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2015:


	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	—	$	20,370	$	—	$	20,370
U.S. government agencies and securities		1,021		—		—		1,021
Corporate bonds		—		33,178		—		33,178

Total assets	$	1,021	$	53,548	$	—	$	54,569

Liabilities:
Derivative instruments	$	—	$	—	$	134	$	134

Total liabilities	$	—	$	—	$	134	$	134

There were no changes in the levels or methodology of measurement of financial assets and liabilities during the three-month period ended March 31, 2015.


	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	—	$	23,692	$	—	$	23,692
Commercial paper		—		1,800		—		1,800
U.S. government agencies and securities		3,022		—		—		3,022
Corporate bonds		—		35,337		—		35,337

Total assets	$	3,022	$	60,829	$	—	$	63,851

Liabilities:
Derivative instruments	$	—	$	—	$	120	$	120
Acquisition-related contingent consideration		—		—		—		—

Total liabilities	$	—	$	—	$	120	$	120

There were no changes in the levels or methodology of measurement of financial assets and liabilities during the twelve months ended December 31, 2014.

Derivative Instruments. Vested non-employee options historically issued by the Company are accounted for as derivative liabilities and remeasured at fair value through earnings at each reporting period until exercised or forfeited. The Black-Scholes model is used to estimate the fair value of these options at each reporting date using the Company’s stock price and an assumed risk-free interest rate, contractual life, expected volatility and dividend yield. Due to the lack of certain observable market quotes, the Company utilizes valuation models that rely on some Level 3 inputs. The Company’s estimate of volatility is based on the Company’s trading history.

The fair value of the Level 3 liabilities is estimated using the Black-Scholes model including the following assumptions:


	As of March 31, 2015			As of December 31, 2014
Risk free interest rate		0.13	%		0.07	%
Expected life of option (years)		0.46			0.70
Expected volatility of stock		38.00	%		39.91	%
Dividend yield		0.00	%		0.00	%

In accordance with ASC 820, the following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for derivative instruments as of March 31, 2015:


Beginning Balance—January 1, 2015	$	120
Total losses included in earnings		14
Exercises		—
Reclassification from equity to liability when fully vested		—

Ending Balance—March 31, 2015	$	134

In accordance with ASC 820, the following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for derivative instruments as of December 31, 2014:


Beginning Balance—January 1, 2014	$	350
Total gains included in earnings		(183	)
Exercises		(47	)
Reclassification from equity to liability when fully vested		—

Ending Balance—December 31, 2014	$	120

Acquisition-Related Contingent Consideration. The Company acquired Endoscopic Technologies, Inc. (Estech) on December 31, 2013. The aggregate consideration paid to Estech shareholders includes up to $26,000 of contingent consideration to be paid based on the achievement of certain performance-based milestones in 2014 and 2015. The fair value of the contingent consideration was estimated using an expected present value approach to estimate an expected value, which, in statistical terms, is the weighted average of a discrete random variable’s possible values with the respective probabilities as the weights. This fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement within the fair value hierarchy. Using this valuation technique, the fair value of the contingent consideration was determined to be $0 as of both March 31, 2015 and December 31, 2014.

The following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for acquisition-related contingent consideration as of December 31, 2014:


Beginning Balance—January 1, 2014	$	8,032
Amounts acquired		—
Transfers in (out) of Level 3		—
Changes in fair value included in earnings		(8,032	)

Ending Balance—December 31, 2014	$	—

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Intangible Assets

3 Months Ended

Mar. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

4. INTANGIBLE ASSETS

The following table provides a summary of the Company’s intangible assets with definite lives:


	March 31, 2015				December 31, 2014
	Cost		Accumulated Amortization		Cost		Accumulated Amortization
Non-compete agreement	$	100	$	96	$	100	$	93
Fusion technology		9,242		1,155		9,242		924
Clamp & probe technology		829		345		829		276
Estech trade name		208		208		208		208

Total	$	10,379	$	1,804	$	10,379	$	1,501

Amortization expense related to intangible assets with definite lives was $303 and $355 for the three months ended March 31, 2015 and 2014, respectively.

Future amortization expense related to intangible assets with definite lives is projected as follows:


2015	$	905	April 1, 2015 through December 31, 2015
2016		1,201
2017		924
2018		924
2019		924
2020 and thereafter		3,697

Total	$	8,575

Accrued Liabilities

3 Months Ended

Mar. 31, 2015

Payables and Accruals [Abstract]

Accrued Liabilities

5. ACCRUED LIABILITIES

Accrued liabilities consisted of the following:


	March 31, 2015		December 31, 2014
Accrued commissions	$	2,975	$	4,477
Accrued payroll and employee-related expenses		2,467		2,281
Accrued bonus		1,636		4,915
Accrued taxes and value-added taxes payable		814		1,272
Accrued royalties		540		442
Other accrued liabilities		276		399
Accrued non-employee stock options		134		120
Sales returns allowance		132		135

Total	$	8,974	$	14,041

Indebtedness

3 Months Ended

Mar. 31, 2015

Debt Disclosure [Abstract]

Indebtedness

6. INDEBTEDNESS

The Company has a debt agreement with Silicon Valley Bank (SVB). The agreement, as amended, restated and modified, includes a $15,000 revolving credit facility which matures on April 30, 2018. Borrowing availability under the revolving credit facility is based on the lesser of $15,000 or a borrowing base calculation as defined by the agreement. As of March 31, 2015 the Company had no borrowings under the revolving credit facility and had borrowing availability of approximately $14,074.

Effective March 31, 2015, the Company and SVB entered into an Eighth Loan Modification Agreement (Loan Modification Agreement) which sets forth certain amendments to the Company’s credit facility. The Loan Modification Agreement provides for (i) an increase in the limit of outstanding letters of credit from $1,000 to $2,000, (ii) an extension of the revolving line maturity date from April 30, 2016 to April 30, 2018 and (iii) modifications to certain covenants and other terms of the agreement.

As of March 31, 2015 and December 31, 2014 the Company had an outstanding letter of credit of €75 issued to its European subsidiary’s corporate credit card program provider which will expire on June 30, 2015.

As of March 31, 2015 the Company had capital leases for computer and office equipment that expire at various terms through 2020. The cost of the assets under lease was $197. The assets are depreciated over their estimated useful lives, which equal the terms of the leases. Accumulated amortization on the capital leases was $71 at March 31, 2015.

Future maturities on capital lease obligations are projected as follows:


2015	$	39		April 1, 2015 through December 31, 2015
2016		52
2017		32
2018		18
2019		8
2020		2

Total payments	$	151
Imputed interest		(12	)

Net capital lease obligations	$	139

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. COMMITMENTS AND CONTINGENCIES *Lease Commitments* The Company leases various types of office, manufacturing and warehouse facilities and equipment under noncancelable operating leases that expire at various terms through 2021. In August 2014 the Company and LM-VP AtriCure, LLC (Landlord), a third party unrelated to the Company, entered into a new building lease (Mason Lease) in order to re-locate its headquarters and West Chester, Ohio facilities from their current location to a building to be constructed on Innovation Way in Mason, Ohio and occupied exclusively by the Company. The term of the Mason Lease is fifteen years with three separate five-year renewal options, at the Company’s option, and begins upon substantial completion of the construction of the building (Commencement Date). The amount of initial annual base rent of $1,353 is payable monthly beginning on the Commencement Date and is subject to a 2% increase each year during the Lease’s initial term. Upon each renewal, the amount of rent payable will be agreed upon by the Company and Landlord or, if not so agreed upon, by an appraiser. The size of the building subject to the Lease is expected to be approximately 92 square feet. Under the Mason Lease, the Company is responsible for paying real estate taxes, insurance, utilities, operating expenses and most building repairs and maintenance. The Company is also responsible for paying the first $750 of construction-related tenant improvement costs, as well as amounts in excess of the estimated total cost of construction, as defined by the Mason Lease. On the Commencement Date, the Company is required to provide a letter of credit to the Landlord in the amount of $1,250, which amount may decrease or be removed entirely based on the Company’s financial performance. The Company is deemed the owner of the project during the construction period. As a result, approximately $5,936 and $3,941 of project costs incurred to date to construct the building are included in property and equipment and the financing obligation is included in other current liabilities in the Condensed Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014, respectively. An increase in purchases of building under construction and proceeds from the construction financing obligation were also included in the Condensed Consolidated Statement of Cash Flows as of March 31, 2015. *Royalty Agreements* The Company has certain royalty agreements in place with terms that include payment of royalties based on product revenue from sales of specified current products. The royalty agreements have effective dates as early as 2003 and terms ranging from three years to at least twenty years. The royalties range from 0.75% to 5% of specified product sales. One of the agreements includes minimum quarterly payments of $50 through 2015 and a maximum of $2,000 in total royalties over the term of the agreement. Parties to the royalty agreements have the right at any time to terminate the agreement immediately for cause. Royalty expense of $427 and $307 was recorded as part of cost of revenue for the three months ended March 31, 2015 and 2014, respectively. *Purchase Agreements* The Company enters into standard purchase agreements with certain vendors in the ordinary course of business. Outstanding commitments at March 31, 2015 were not significant. *Legal* The Company may, from time to time, become a party to legal proceedings.

Income Tax Provision	3 Months Ended
Income Tax Provision	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Tax Provision	8. INCOME TAX PROVISION The Company files federal, state, and foreign income tax returns in jurisdictions with varying statutes of limitations. Income taxes are computed using the asset and liability method in accordance with FASB ASC 740, “Income Taxes”, under which deferred income taxes are provided for the temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities. Deferred taxes are measured using provisions of currently enacted tax laws. A valuation allowance against deferred tax assets is recorded when it is more-likely-than-not that such assets will not be fully realized. The Company has recorded a full valuation allowance against its net deferred tax assets as it is more-likely-than-not that the benefit of the deferred tax assets will not be recognized in future periods. Tax credits are accounted for as a reduction of income taxes in the year in which the credit originates. The Company does not expect any significant unrecognized tax benefits to arise over the next twelve months. The Company’s provision for income taxes for continuing operations in interim periods is computed by applying its estimated annual effective rate against its loss before income tax (expense) benefit for the period. In addition, non-recurring or discrete items are recorded during the period in which they occur. The effective tax rate for the three months ended March 31, 2015 and 2014 was (0.11%) and (0.35%), respectively. The Company has not had to accrue any interest and penalties related to unrecognized income tax benefits as a result of offsetting of net operating losses. However, if the situation occurs, the Company will recognize interest and penalties within the income tax expense (benefit) line in the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss and within the related tax liability line in the Condensed Consolidated Balance Sheets.

Equity Compensation Plans

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity Compensation Plans

9. EQUITY COMPENSATION PLANS

The Company has several share-based incentive plans: the 2001 Stock Option Plan (2001 Plan), the 2005 Equity Incentive Plan (2005 Plan), the Amended and Restated 2014 Stock Incentive Plan (2014 Plan) and the 2008 Employee Stock Purchase Plan (ESPP).

2001 Plan, 2005 Plan and 2014 Plan

Neither the 2001 Plan nor 2005 Plan is currently used for granting incentives. The Company granted awards under the 2005 Plan until the 2014 Annual Meeting of Stockholders at which stockholders adopted the 2014 Plan. Pursuant to its terms, the 2014 Plan supersedes and replaces the 2005 Plan. Under the 2014 Plan, the Board of Directors may grant incentive stock options to employees and any parent or subsidiary’s employees, and may grant nonstatutory stock options, restricted stock or stock appreciation rights to employees, directors and consultants of the Company and any parent or subsidiary’s employees, directors and consultants. The administrator (currently the Compensation Committee of the Board of Directors) has the power to determine the terms of any awards, including the exercise price of options, the number of shares subject to each award, the exercisability of the awards and the form of consideration. As of March 31, 2015 8,949 shares of common stock had been reserved for issuance under the 2014 Plan.

Options granted under the plans generally expire ten years from the date of grant. Options granted from the 2005 Plan and 2014 Plan generally vest at a rate of 25% on the first anniversary date of the grant and ratably each month thereafter over the following three years. Restricted stock awards granted under the 2005 Plan and 2014 Plan generally vest 25% annually over four years from date of grant.

Employee Stock Purchase Plan (ESPP)

During 2008 the Company established the Employee Stock Purchase Plan which is available to eligible employees as defined in the ESPP. Under the ESPP, shares of the Company’s common stock may be purchased at a discount (currently 15%) of the lesser of the closing price of the Company’s common stock on the first trading day or the last trading day of the offering period. The offering period (currently six months) and the offering price are subject to change. Participants may not purchase more than $25 of the Company’s common stock in a calendar year and, effective January 1, 2014, may not purchase more than 3 shares during an offering period. Beginning on January 1, 2009 and on the first day of each fiscal year thereafter during the term of the ESPP, the number of shares available for sale under the ESPP shall be increased by the lesser of (i) two percent (2%) of the Company’s outstanding shares of common stock as of the close of business on the last business day of the prior calendar year, not to exceed 600 shares, or (ii) a lesser amount determined by the Board of Directors. At March 31, 2015 there were 578 shares available for future issuance under the ESPP.

Valuation and Expense Information Under FASB ASC 718

The following table summarizes share-based compensation expense related to employee share-based compensation under FASB ASC 718 for the three months ended March 31, 2015 and 2014. This expense was allocated as follows:


	Three Months Ended March 31,
	2015		2014
Cost of revenue	$	90	$	71
Research and development expenses		289		132
Selling, general and administrative expenses		1,345		1,939

Total share-based compensation expense related to employees	$	1,724	$	2,142

Segment and Geographic Information

3 Months Ended

Mar. 31, 2015

Segment Reporting [Abstract]

Segment and Geographic Information

10. SEGMENT AND GEOGRAPHIC INFORMATION

The Company evaluates reporting segments in accordance with FASB ASC 280, “Segment Reporting”. The Company develops, manufactures, and sells devices designed primarily for the surgical ablation of cardiac tissue and systems designed for the exclusion of the left atrial appendage. These devices are developed and marketed to a broad base of medical centers in the United States and internationally. Management considers all such sales to be part of a single reportable segment. Revenue attributed to geographic areas is based on the location of the customers to whom products are sold.

Revenue by geographic area was as follows:


	Three Months Ended March 31,
	2015		2014
United States	$	22,923	$	18,143

Europe		4,416		4,308
Asia		2,300		2,292
Other international		247		104

Total international		6,963		6,704


Total revenue	$	29,886	$	24,847

Domestic revenue by product type was as follows:


	Three Months Ended March 31,
	2015		2014
Open-heart ablation	$	12,354	$	10,377
Minimally invasive ablation		4,347		3,448
AtriClip		5,503		3,620

Total ablation and AtriClip		22,204		17,445
Valve tools		719		698

Total domestic	$	22,923	$	18,143

International revenue by product type was as follows:


	Three Months Ended March 31,
	2015		2014
Open-heart ablation	$	4,216	$	3,971
Minimally invasive ablation		1,968		2,003
AtriClip		671		443

Total ablation and AtriClip		6,855		6,417
Valve tools		108		287

Total international	$	6,963	$	6,704

The majority of the Company’s long-lived assets are located in the United States.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Public Offerings of Common Stock	3 Months Ended
Public Offerings of Common Stock	Mar. 31, 2015
Equity [Abstract]
Public Offerings of Common Stock	11. PUBLIC OFFERINGS OF COMMON STOCK In February 2014 the Company completed a public offering of common stock under its January 2014 shelf registration. The Company sold 3,661 shares of common stock, par value $0.001 per share, at a price of $19.25 per share, generating proceeds of $65,830 after expenses. Offering costs were recorded in additional paid in capital to offset proceeds.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Description of Business and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2015

Accounting Policies [Abstract]

Nature of the Business

Basis of Presentation

Principles of Consolidation

Cash and Cash Equivalents

Cash and Cash Equivalents—The Company considers highly liquid investments with maturities of three months or less at the date of acquisition as cash equivalents.

Investments

Revenue Recognition

Sales Returns and Allowances

Allowance for Doubtful Accounts Receivable

Inventories

Inventories consist of the following:


	March 31, 2015		December 31, 2014
Raw materials	$	4,484	$	4,429
Work in process		1,169		1,397
Finished goods		9,453		8,431

Inventories	$	15,106	$	14,257

Property and Equipment

The Company reviews property and equipment for impairment using its best estimates based on reasonable and supportable assumptions and projections.

Intangible Assets

Goodwill

Other Current Liabilities and Current Maturities of Capital Leases

Other Income

Taxes

Net Loss Per Share

Comprehensive Loss and Accumulated Other Comprehensive Loss

Accumulated other comprehensive income (loss) consisted of the following:


	Three Months Ended March 31,
	2015			2014
Total accumulated other comprehensive loss at beginning of period	$	(348	)	$	(139	)

Unrealized Loss on Investments
Balance at beginning of period	$	(54	)	$	(6	)
Other comprehensive income (loss) before reclassifications		37			(2	)
Amounts reclassified from accumulated other comprehensive income (loss) to other income		—			—

Balance at end of period	$	(17	)	$	(8	)


Foreign Currency Translation Adjustment
Balance at beginning of period	$	(294	)	$	(133	)
Other comprehensive loss before reclassifications		(324	)		(3	)
Amounts reclassified from accumulated other comprehensive loss to other income (expense)		(163	)		5

Balance at end of period	$	(781	)	$	(131	)


Total accumulated other comprehensive loss at end of period	$	(798	)	$	(139	)

Research and Development

Advertising Costs

Advertising Costs—The Company expenses advertising costs as incurred. Advertising costs were not significant during the three months ended March 31, 2015 and 2014.

Share-Based Compensation

Use of Estimates

Fair Value Disclosures

Description of Business and Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2015

Accounting Policies [Abstract]

Summary of Inventories

Inventories consist of the following:


	March 31, 2015		December 31, 2014
Raw materials	$	4,484	$	4,429
Work in process		1,169		1,397
Finished goods		9,453		8,431

Inventories	$	15,106	$	14,257

Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) consisted of the following:


	Three Months Ended March 31,
	2015			2014
Total accumulated other comprehensive loss at beginning of period	$	(348	)	$	(139	)

Unrealized Loss on Investments
Balance at beginning of period	$	(54	)	$	(6	)
Other comprehensive income (loss) before reclassifications		37			(2	)
Amounts reclassified from accumulated other comprehensive income (loss) to other income		—			—

Balance at end of period	$	(17	)	$	(8	)


Foreign Currency Translation Adjustment
Balance at beginning of period	$	(294	)	$	(133	)
Other comprehensive loss before reclassifications		(324	)		(3	)
Amounts reclassified from accumulated other comprehensive loss to other income (expense)		(163	)		5

Balance at end of period	$	(781	)	$	(131	)


Total accumulated other comprehensive loss at end of period	$	(798	)	$	(139	)

Fair Value (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis


	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	—	$	20,370	$	—	$	20,370
U.S. government agencies and securities		1,021		—		—		1,021
Corporate bonds		—		33,178		—		33,178

Total assets	$	1,021	$	53,548	$	—	$	54,569

Liabilities:
Derivative instruments	$	—	$	—	$	134	$	134

Total liabilities	$	—	$	—	$	134	$	134

There were no changes in the levels or methodology of measurement of financial assets and liabilities during the three-month period ended March 31, 2015.


	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	—	$	23,692	$	—	$	23,692
Commercial paper		—		1,800		—		1,800
U.S. government agencies and securities		3,022		—		—		3,022
Corporate bonds		—		35,337		—		35,337

Total assets	$	3,022	$	60,829	$	—	$	63,851

Liabilities:
Derivative instruments	$	—	$	—	$	120	$	120
Acquisition-related contingent consideration		—		—		—		—

Total liabilities	$	—	$	—	$	120	$	120

Assumptions Used for Estimating Fair Value of Level 3 Liabilities

The fair value of the Level 3 liabilities is estimated using the Black-Scholes model including the following assumptions:


	As of March 31, 2015			As of December 31, 2014
Risk free interest rate		0.13	%		0.07	%
Expected life of option (years)		0.46			0.70
Expected volatility of stock		38.00	%		39.91	%
Dividend yield		0.00	%		0.00	%

Level 3 Fair Value Measurements Using Significant Other Unobservable Inputs for Derivative Instruments

In accordance with ASC 820, the following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for derivative instruments as of March 31, 2015:


Beginning Balance—January 1, 2015	$	120
Total losses included in earnings		14
Exercises		—
Reclassification from equity to liability when fully vested		—

Ending Balance—March 31, 2015	$	134


Beginning Balance—January 1, 2014	$	350
Total gains included in earnings		(183	)
Exercises		(47	)
Reclassification from equity to liability when fully vested		—

Ending Balance—December 31, 2014	$	120

Level 3 Fair Value Measurements Using Significant Other Unobservable Inputs for Acquisition Related Contingent Consideration

The following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for acquisition-related contingent consideration as of December 31, 2014:


Beginning Balance—January 1, 2014	$	8,032
Amounts acquired		—
Transfers in (out) of Level 3		—
Changes in fair value included in earnings		(8,032	)

Ending Balance—December 31, 2014	$	—

Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Company's Intangible Assets with Definite Lives

The following table provides a summary of the Company’s intangible assets with definite lives:


	March 31, 2015				December 31, 2014
	Cost		Accumulated Amortization		Cost		Accumulated Amortization
Non-compete agreement	$	100	$	96	$	100	$	93
Fusion technology		9,242		1,155		9,242		924
Clamp & probe technology		829		345		829		276
Estech trade name		208		208		208		208

Total	$	10,379	$	1,804	$	10,379	$	1,501

Future Amortization Expense Related to Intangible Assets with Definite Lives

Future amortization expense related to intangible assets with definite lives is projected as follows:


2015	$	905	April 1, 2015 through December 31, 2015
2016		1,201
2017		924
2018		924
2019		924
2020 and thereafter		3,697

Total	$	8,575

Accrued Liabilities (Tables)

3 Months Ended

Mar. 31, 2015

Payables and Accruals [Abstract]

Accrued Liabilities

Accrued liabilities consisted of the following:


	March 31, 2015		December 31, 2014
Accrued commissions	$	2,975	$	4,477
Accrued payroll and employee-related expenses		2,467		2,281
Accrued bonus		1,636		4,915
Accrued taxes and value-added taxes payable		814		1,272
Accrued royalties		540		442
Other accrued liabilities		276		399
Accrued non-employee stock options		134		120
Sales returns allowance		132		135

Total	$	8,974	$	14,041

Indebtedness (Tables)

3 Months Ended

Mar. 31, 2015

Debt Disclosure [Abstract]

Future Maturities on Debt, Including Capital Lease Obligations

Future maturities on capital lease obligations are projected as follows:


2015	$	39		April 1, 2015 through December 31, 2015
2016		52
2017		32
2018		18
2019		8
2020		2

Total payments	$	151
Imputed interest		(12	)

Net capital lease obligations	$	139

Equity Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Share-Based Compensation Expense Related to Employee Share-Based Compensation


	Three Months Ended March 31,
	2015		2014
Cost of revenue	$	90	$	71
Research and development expenses		289		132
Selling, general and administrative expenses		1,345		1,939

Total share-based compensation expense related to employees	$	1,724	$	2,142

Segment and Geographic Information (Tables)

3 Months Ended

Mar. 31, 2015

Segment Reporting [Abstract]

Summary of Revenue by Geographic Area

Revenue by geographic area was as follows:


	Three Months Ended March 31,
	2015		2014
United States	$	22,923	$	18,143

Europe		4,416		4,308
Asia		2,300		2,292
Other international		247		104

Total international		6,963		6,704


Total revenue	$	29,886	$	24,847

Revenue by Product

Domestic revenue by product type was as follows:


	Three Months Ended March 31,
	2015		2014
Open-heart ablation	$	12,354	$	10,377
Minimally invasive ablation		4,347		3,448
AtriClip		5,503		3,620

Total ablation and AtriClip		22,204		17,445
Valve tools		719		698

Total domestic	$	22,923	$	18,143

International revenue by product type was as follows:


	Three Months Ended March 31,
	2015		2014
Open-heart ablation	$	4,216	$	3,971
Minimally invasive ablation		1,968		2,003
AtriClip		671		443

Total ablation and AtriClip		6,855		6,417
Valve tools		108		287

Total international	$	6,963	$	6,704

Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Description Of Business And Significant Accounting Policies [Line Items]
Maturity period of short term investment	1 year
Shipping and handling revenue	$ 247	$ 227
Payment terms for end-users	30 days
Payment terms for distributors	60 days
Depreciation	$ 1,008	730
Net carrying amount of loaned equipment	13,874		$ 11,552
Net foreign currency transaction (losses) gains	(487)	2
Grant income	35	363
(Income) expense related to remeasurement of fair value of fully vested stock options	13	(98)
Company's expense related to the medical device excise tax	$ 155	$ 114
Options, restricted stock and performance based shares excluded from calculation of net loss per share	4,320	3,762
Share-based compensation expense recognized	$ 1,724	$ 2,142
Subsidiaries [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Net foreign currency transaction (losses) gains	$ (163)	5
Computer and Other Office Equipment [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Estimated useful life by major asset category	3 years
Generators [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Depreciation	$ 620	$ 461
Carrying Amount of Loaned Equipment [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Net carrying amount of loaned equipment	$ 4,123		$ 4,141
Minimum [Member] \| Generators and Other Capital Equipment, Machinery, Equipment and Vehicles [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Estimated useful life by major asset category	3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Estimated useful life by major asset category	3 years
Maximum [Member] \| Generators and Other Capital Equipment, Machinery, Equipment and Vehicles [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Estimated useful life by major asset category	7 years
Maximum [Member] \| Furniture and Fixtures [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Estimated useful life by major asset category	7 years

Description of Business and Summary of Significant Accounting Policies - Summary of Inventories (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials	$ 4,484	$ 4,429
Work in process	1,169	1,397
Finished goods	9,453	8,431
Inventories	$ 15,106	$ 14,257

Description of Business and Summary of Significant Accounting Policies - Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (348)	$ (139)
Ending Balance	(798)	(139)
Unrealized Loss on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(54)	(6)
Other comprehensive income (loss) before reclassifications	37	(2)
Ending Balance	(17)	(8)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(294)	(133)
Other comprehensive income (loss) before reclassifications	(324)	(3)
Amounts reclassified from accumulated other comprehensive loss to other income (expense)	(163)	5
Ending Balance	$ (781)	$ (131)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

Fair Value - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Significant Other Unobservable Inputs (Level 3) [Member]
Liabilities:
Acquisition-related contingent consideration	$ 0	$ 0
Fair Value, Measurements, Recurring [Member]
Assets:
Total assets	54,569	63,851
Liabilities:
Derivative instruments	134	120
Acquisition-related contingent consideration		0
Total liabilities	134	120
Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member]
Assets:
Total assets	20,370	23,692
Fair Value, Measurements, Recurring [Member] \| Commercial Paper [Member]
Assets:
Total assets		1,800
Fair Value, Measurements, Recurring [Member] \| U.S. Government Agencies and Securities [Member]
Assets:
Total assets	1,021	3,022
Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Assets:
Total assets	33,178	35,337
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Total assets	1,021	3,022
Liabilities:
Acquisition-related contingent consideration		0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| U.S. Government Agencies and Securities [Member]
Assets:
Total assets	1,021	3,022
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total assets	53,548	60,829
Liabilities:
Acquisition-related contingent consideration		0
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Money Market Funds [Member]
Assets:
Total assets	20,370	23,692
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Commercial Paper [Member]
Assets:
Total assets		1,800
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member]
Assets:
Total assets	33,178	35,337
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) [Member]
Liabilities:
Derivative instruments	134	120
Acquisition-related contingent consideration		0
Total liabilities	$ 134	$ 120

Fair Value - Assumptions Used for Estimating Fair Value of Level 3 Liabilities (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Risk free interest rate	0.13%	0.07%
Expected life of option (years)	5 months 16 days	8 months 12 days
Expected volatility of stock	38.00%	39.91%
Dividend yield	0.00%	0.00%

Fair Value - Level 3 Fair Value Measurements Using Significant Other Unobservable Inputs for Derivative Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Beginning Balance	$ 120	$ 350
Total (gains) losses included in earnings	14	(183)
Exercises		(47)
Reclassification from equity to liability when fully vested	0	0
Ending Balance	$ 134	$ 120

Fair Value - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Other Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration	$ 0	$ 0
Maximum [Member] \| Estech [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration			$ 26,000

Fair Value - Level 3 Fair Value Measurements Using Significant Other Unobservable Inputs for Acquisition Related Contingent Consideration (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($)
Debt Instrument Fair Value Carrying Value [Abstract]
Beginning Balance	$ 8,032
Amounts acquired	0
Transfers in (out) of Level 3	0
Changes in fair value included in earnings	(8,032)
Ending Balance	$ 0

Intangible Assets - Summary of Company's Intangible Assets with Definite Lives (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Cost	$ 10,379	$ 10,379
Accumulated Amortization	1,804	1,501
Non-Compete Agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	100	100
Accumulated Amortization	96	93
Fusion Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	9,242	9,242
Accumulated Amortization	1,155	924
Clamp and Probe Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	829	829
Accumulated Amortization	345	276
Estech Trade Name [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	208	208
Accumulated Amortization	$ 208	$ 208

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 303	$ 355

Intangible Assets - Future Amortization Expense Related to Intangible Assets with Definite Lives (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Expected amortization expense April 1, 2015 through December 31, 2015	$ 905
Expected amortization expense in 2016	1,201
Expected amortization expense in 2017	924
Expected amortization expense in 2018	924
Expected amortization expense in 2019	924
Expected amortization expense in 2020 and thereafter	3,697
Total	$ 8,575	$ 8,878

Accrued Liabilities - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued commissions	$ 2,975	$ 4,477
Accrued payroll and employee-related expenses	2,467	2,281
Accrued bonus	1,636	4,915
Accrued taxes and value-added taxes payable	814	1,272
Accrued royalties	540	442
Other accrued liabilities	276	399
Accrued non-employee stock options	134	120
Sales returns allowance	132	135
Total	$ 8,974	$ 14,041

Indebtedness - Additional Information (Detail) € in Thousands			3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2015 EUR (€)	Dec. 31, 2014 EUR (€)
Credit Facilities [Line Items]
Letter of credit outstanding \| €				€ 75	€ 75
Expiry of outstanding letter of credit			Jun. 30, 2015
Capital lease expiration period			2020
Cost of assets under lease	$ 197,000		$ 197,000
Accumulated amortization on the capital leases	71,000		71,000
Revolving Credit Facility [Member]
Credit Facilities [Line Items]
Credit facility	15,000,000		$ 15,000,000
Letter of credit maturity date			Apr. 30, 2018
Borrowings under the revolving credit facility, availability			$ 14,074,000
Borrowings under the revolving credit facility, outstanding	$ 0		0
Eighth Loan Modification Agreement [Member]
Credit Facilities [Line Items]
Letter of credit maturity date	Apr. 30, 2018	Apr. 30, 2016
Outstanding letters of credit limit	$ 2,000,000	$ 1,000,000	$ 2,000,000

Indebtedness - Future Maturities on Debt, Including Capital Lease Obligations (Detail) $ in Thousands	Mar. 31, 2015 USD ($)
Debt Disclosure [Abstract]
Capital lease obligations due April 1, 2015 through December 31, 2015	$ 39
Capital lease obligations due 2016	52
Capital lease obligations due 2017	32
Capital lease obligations due 2018	18
Capital lease obligations due 2019	8
Capital lease obligations due thereafter	2
Capital lease obligations total payments	151
Imputed interest	(12)
Net capital lease obligations	$ 139

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2015 USD ($) ft² Lease	Mar. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)
Commitments and Contingencies [Line Items]
Operating leases expire at various terms	2021
Letter of credit to be issued to landlord, amount	$ 1,250
Royalty expense	$ 427	$ 307
Minimum [Member]
Commitments and Contingencies [Line Items]
Royalty rates	0.75%
Royalty payments	$ 50
Royalty agreement term	3 years
Maximum [Member]
Commitments and Contingencies [Line Items]
Royalty rates	5.00%
Royalty payments	$ 2,000
Royalty agreement term	20 years
Mason Lease [Member]
Commitments and Contingencies [Line Items]
Lease term period	15 years
Number of renewal options \| Lease	3
Lease renewal option period	5 years
Initial annual base rent	$ 1,353
Lease rate increase, percentage	2.00%
Area of lease \| ft²	92
Project cost included in the construction of building	$ 5,936		$ 3,941
Mason Lease [Member] \| Leasehold Improvements [Member]
Commitments and Contingencies [Line Items]
Leases payable, amount	$ 750

Income Tax Provision - Additional Information (Detail)	3 Months Ended
Income Tax Provision - Additional Information (Detail)	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Effective tax rate	0.11%	0.35%

Equity Compensation Plans - 2001 Plan, 2005 Plan and 2014 Plan - Additional Information (Detail) shares in Thousands	3 Months Ended
	Mar. 31, 2015 shares
2001 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of options from the date of grant	10 years
2005 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of options from the date of grant	10 years
Restricted stock awards granted annual vest rate	25.00%
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of options from the date of grant	10 years
Restricted stock awards granted annual vest rate	25.00%
Common stock reserved for issuance	8,949
Employee Stock Option [Member] \| 2005 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period beginning	3 years
Options granted exercisable cumulative	25.00%
Employee Stock Option [Member] \| 2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period beginning	3 years
Options granted exercisable cumulative	25.00%
Restricted Stock [Member] \| 2005 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted from the 2005 Plan generally vest	4 years
Restricted Stock [Member] \| 2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted from the 2005 Plan generally vest	4 years

Equity Compensation Plans - Employee Stock Purchase Plan - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2015 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Description of participants purchase limit	Participants may not purchase more than $25 of the Company's common stock in a calendar year and, effective January 1, 2014, may not purchase more than 3 shares during an offering period
Participants purchase limit shares	3,000
Offering period	6 months
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company's common stock may be purchased at a discount	15.00%
Participants purchase limit value \| $	$ 25
Shares available for sale under the ESPP increased	2.00%
Outstanding shares of common stock exceed	600,000
Shares available for future issuance under the ESPP	578,000

Equity Compensation Plans - Summary of Share-Based Compensation Expense Related to Employee Share-Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense related to employees	$ 1,724	$ 2,142
Cost of Revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense related to employees	90	71
Research and Development Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense related to employees	289	132
Selling, General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense related to employees	$ 1,345	$ 1,939

Segment and Geographic Information - Summary of Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Information About Revenue And Geographic Areas [Line Items]
Revenue	$ 29,886	$ 24,847
United States [Member]
Information About Revenue And Geographic Areas [Line Items]
Revenue	22,923	18,143
Europe [Member]
Information About Revenue And Geographic Areas [Line Items]
Revenue	4,416	4,308
Asia [Member]
Information About Revenue And Geographic Areas [Line Items]
Revenue	2,300	2,292
Other International [Member]
Information About Revenue And Geographic Areas [Line Items]
Revenue	247	104
International [Member]
Information About Revenue And Geographic Areas [Line Items]
Revenue	$ 6,963	$ 6,704

Segment and Geographic Information - Revenue by Product (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Product Type Reporting Information [Line Items]
Revenue	$ 29,886	$ 24,847
United States [Member]
Product Type Reporting Information [Line Items]
Revenue	22,923	18,143
United States [Member] \| Open-heart Ablation [Member]
Product Type Reporting Information [Line Items]
Revenue	12,354	10,377
United States [Member] \| Minimally Invasive Ablation [Member]
Product Type Reporting Information [Line Items]
Revenue	4,347	3,448
United States [Member] \| AtriClip [Member]
Product Type Reporting Information [Line Items]
Revenue	5,503	3,620
United States [Member] \| Ablation and AtriClip [Member]
Product Type Reporting Information [Line Items]
Revenue	22,204	17,445
United States [Member] \| Valve Tools [Member]
Product Type Reporting Information [Line Items]
Revenue	719	698
International [Member]
Product Type Reporting Information [Line Items]
Revenue	6,963	6,704
International [Member] \| Open-heart Ablation [Member]
Product Type Reporting Information [Line Items]
Revenue	4,216	3,971
International [Member] \| Minimally Invasive Ablation [Member]
Product Type Reporting Information [Line Items]
Revenue	1,968	2,003
International [Member] \| AtriClip [Member]
Product Type Reporting Information [Line Items]
Revenue	671	443
International [Member] \| Ablation and AtriClip [Member]
Product Type Reporting Information [Line Items]
Revenue	6,855	6,417
International [Member] \| Valve Tools [Member]
Product Type Reporting Information [Line Items]
Revenue	$ 108	$ 287

Public Offerings of Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2014	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Common stock sold	3,661
Common stock, par value	$ 0.001		$ 0.001	$ 0.001
Common stock, price per share	$ 19.25
Proceeds from issuance of common stock	$ 65,830	$ 65,872