AtriCure (ATRC) 10-Q 2 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	ATRC
Entity Registrant Name	AtriCure, Inc.
Entity Central Index Key	1,323,885
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		35,361,743

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 13,866	$ 21,809
Short-term investments	23,202	12,642
Accounts receivable, less allowance for doubtful accounts of $32 and $32	24,895	23,083
Inventories	21,682	22,451
Other current assets	3,120	2,273
Total current assets	86,765	82,258
Property and equipment, net	28,126	28,749
Intangible assets, net	50,080	50,764
Goodwill	105,257	105,257
Other noncurrent assets	619	676
Total Assets	270,847	267,704
Current liabilities:
Accounts payable	9,670	12,431
Accrued liabilities	17,161	18,911
Other current liabilities and current maturities of capital leases	589	561
Total current liabilities	27,420	31,903
Capital leases	12,492	12,761
Long-term debt	39,399	24,100
Other noncurrent liabilities	31,849	37,774
Total Liabilities	111,160	106,538
Commitments and contingencies (Note 7)
Stockholders' Equity:
Common stock, $0.001 par value, 90,000 shares authorized and 35,313 and 34,586 issued and outstanding	35	35
Additional paid-in capital	396,088	386,963
Accumulated other comprehensive (loss) income	(98)	34
Accumulated deficit	(236,338)	(225,866)
Total Stockholders' Equity	159,687	161,166
Total Liabilities and Stockholders' Equity	$ 270,847	$ 267,704

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Condensed Consolidated Balance Sheets [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 32	$ 32
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	35,313,000	34,586,000
Common stock, shares outstanding	35,313,000	34,586,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Consolidated Statements of Operations and Comprehensive Loss [Abstract]
Revenue	$ 51,802	$ 45,231	$ 98,796	$ 86,504
Cost of revenue	13,723	12,677	26,214	23,942
Gross profit	38,079	32,554	72,582	62,562
Operating expenses:
Research and development expenses	8,655	8,907	17,712	18,457
Selling, general and administrative expenses	28,466	30,002	63,342	60,102
Total operating expenses	37,121	38,909	81,054	78,559
Income (Loss) from operations	958	(6,355)	(8,472)	(15,997)
Other income (expense):
Interest expense	(1,221)	(564)	(2,041)	(1,118)
Interest income	123	48	199	102
Other	(150)	5	(62)	(13)
Loss before income tax expense	(290)	(6,866)	(10,376)	(17,026)
Income tax expense	48	17	96	40
Net loss	$ (338)	$ (6,883)	$ (10,472)	$ (17,066)
Basic and diluted net loss per share	$ (0.01)	$ (0.21)	$ (0.32)	$ (0.53)
Weighted average shares outstanding — basic and diluted	33,252	32,288	33,117	32,154
Comprehensive loss:
Unrealized gain (loss) gain on investments	$ 1	$ 4	$ (7)	$ 6
Foreign currency translation adjustment	(211)	342	(125)	415
Other comprehensive (loss) income	(210)	346	(132)	421
Net loss	(338)	(6,883)	(10,472)	(17,066)
Comprehensive loss, net of tax	$ (548)	$ (6,537)	$ (10,604)	$ (16,645)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (10,472)	$ (17,066)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	7,424	7,325
Depreciation	3,719	3,906
Amortization of intangible assets	684	684
Amortization of deferred financing costs	217	132
Loss on disposal of property and equipment	97	88
Realized (gain) loss from foreign exchange on intercompany transactions	56	(10)
(Accretion) amortization of investments	(56)	59
Change in allowance for doubtful accounts	58	(134)
Change in value of contingent consideration	(5,916)
Changes in operating assets and liabilities:
Accounts receivable	(1,946)	(1,673)
Inventories	703	(2,094)
Other current assets	(877)	(26)
Accounts payable	(2,432)	565
Accrued liabilities	(1,697)	(1,891)
Other noncurrent assets and liabilities	69	(468)
Net cash used in operating activities	(10,369)	(10,603)
Cash flows from investing activities:
Purchases of available-for-sale securities	(23,510)	(7,567)
Sales and maturities of available-for-sale securities	13,000	16,350
Purchases of property and equipment	(3,473)	(3,488)
Proceeds from sale of property and equipment	6
Net cash (used in) provided by investing activities	(13,977)	5,295
Cash flows from financing activities:
Proceeds from debt borrowings	17,381
Payments on debt and capital leases	(1,469)	(241)
Payment of debt fees	(1,136)	(50)
Shares repurchased for payment of taxes on stock awards	(3,724)	(1,901)
Proceeds from exercise of stock options and employee stock purchase plan	5,425	4,279
Net cash provided by financing activities	16,477	2,087
Effect of exchange rate changes on cash and cash equivalents	(74)	26
Net decrease in cash and cash equivalents	(7,943)	(3,195)
Cash and cash equivalents-beginning of period	21,809	24,208
Cash and cash equivalents-end of period	13,866	21,013
Supplemental cash flow information:
Cash paid for interest	1,210	985
Cash paid for income taxes	45
Non-cash investing and financing activities:
Accrued purchases of property and equipment	366	703
Assets acquired through capital lease	24
Capital lease asset early termination	$ (6)

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Description of Business and Summary of Significant Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	1. DESC RIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of the Business —The “Company” consists of AtriCure, Inc. and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The Company is a leading innovator in treatments for atrial fibrillation (Afib) and left atrial appendage (LAA) management, and sells its products to medical centers globally through its 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 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 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 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, 2017 filed with the SEC. Cash Equivalents —The Company considers highly liquid investments with maturities of three months or less at the date of purchase as cash equivalents in the accompanying Condensed Consolidated Financial Statements. Investments —The Company invests primarily in U.S. Government securities, corporate bonds, commercial paper and asset-backed securities and 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. Gains and losses are recognized using the specific identification method when securities are sold and are included in interest income or expense in the Condensed Consolidated Statements of Operations and Comprehensive Loss. Revenue Recognition— The Company recognizes revenue when control of promised goods is transferred to customers in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods. This generally occurs upon shipment of goods to customers. See Note 8 for further discussion on revenue. Sales Returns and Allowances —The Company maintains a provision for potential returns of defective or damaged products and products shipped in error and invoice adjustments. The Company adjusts the provision through consideration of a combination of specific identification and historical experience. 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 to determine the appropriate allowance for doubtful accounts considering the aging of accounts, historical credit losses, customer-specific information and other relevant factors. Increases to the allowance result in an increase in selling, general and administrative expenses. The Company 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 net realizable value based on the first-in, first-out cost method (FIFO). The Company’s industry is characterized by rapid product development and frequent new product introductions. Uncertain timing of regulatory approval, variability in product launch strategies and variation in product use cause the Company to maintain reserves for excess, obsolete and expired products. Increases to inventory reserves result in an increase in cost of revenue. Inventories are written off against reserves when they are physically disposed. Inventories consist of the following:      June 30, December 31,  2018 2017  Raw materials $ 8,729 $ 7,755  Work in process 1,549 1,299  Finished goods 11,404 13,397  Inventories $ 21,682 $ 22,451 Property and Equipment —Property and equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of assets. The estimated useful life by major asset category is the following:      Estimated Useful Life  Generators and related equipment 1 - 3 years  Building under capital lease 15 years  Computers, software and office equipment 3 years  Machinery and equipment 3 - 7 years  Furniture and fixtures 3 - 7 years  Leasehold improvements 5 - 15 years  Equipment under capital leases 3 - 5 years The Company reassesses the useful lives of property and equipment at least annually and retires assets if they are no longer in service. Maintenance and repair costs are expensed as incurred. The Company’s radiofrequency (RF) and cryo generators are generally placed with customers that use the Company’s disposable products. The estimated useful lives of generators are based on anticipated usage by customers and may change in future periods with changes in usage or introduction of new technologies. Depreciation related to generators and related equipment, which is recorded in cost of revenue in the Condensed Consolidated Statements of Operations and Comprehensive Loss, was $814 and $909 for the three months ended June 30, 2018 and 2017 and $1,641 and $1,825 for the six months ended June 30, 2018 and 2017 . As of June 30, 2018 and December 31, 2017 , the net carrying value of generators and related equipment included in net property and equipment in the Condensed Consolidated Balance Sheets was $4,717 and $4,656 . The Company reviews property and equipment for impairment at least annually using its best estimates based on reasonable and supportable assumptions and expected future cash flows. Property and equipment impairments recorded by the Company have not been significant. Intangible Assets —Intangible assets with determinable useful lives are amortized on a straight-line basis over the estimated periods benefited. Intangible assets include In-Process Research and Development (IPR&D), which represents the value of technology acquired in business combinations that has not yet reached technological feasibility. The primary basis for determining technological feasibility is obtaining specific regulatory approval. IPR&D is accounted for as an indefinite-lived intangible asset until completion or abandonment of the IPR&D project. Upon completion of the development project, IPR&D will be amortized over its estimated useful life. If the IPR&D project is abandoned, the IPR&D would be written off. IPR&D represents an estimate of the fair value of the pre-market approval (PMA) that may result from the CONVERGE IDE clinical trial. The Company reviews intangible assets for impairment at least annually using its best estimates based on reasonable and supportable assumptions and projections. The Company has historically tested IPR&D for impairment annually on November 30. Goodwill— Goodwill represents the excess of purchase price over the fair value of the net assets acquired in business combinations. The Company has historically tested 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’s consolidated operations. Other Noncurrent Liabilities— Other noncurrent liabilities consist of acquisition-related contingent consideration and other contractual obligations. Although the Company expects to settle a portion of the contingent consideration liability in 2018, the balance is included in noncurrent liabilities as such settlement is both required and expected to be made in shares of the Company’s common stock pursuant to the nContact Surgical, Inc. (nContact) merger agreement. Other Income (Expense) — Other income (expense) consists primarily of foreign currency transaction gains and losses generated by settlements of intercompany balances denominated in Euros and customer invoicing in British Pounds. Taxes —Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred income 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 income 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 income tax assets requires significant estimates and judgments about future operating results. Deferred income tax assets are reduced by valuation allowances if, based on the consideration of all available evidence, it is more-likely-than-not that the deferred income tax asset will not be realized. Significant weight is given to evidence that can be objectively verified. The Company evaluates deferred income tax assets on an annual basis to determine if valuation allowances are required. Deferred income 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 income 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 the need for a valuation allowance, the existence of cumulative losses in recent years is significant 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 substantially all net deferred income tax assets as it is more-likely-than-not that the benefit of the deferred income tax assets will not be recognized in future periods. Net Loss Per Share —Basic and diluted net loss per share is computed 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 4,063 and 4,349 stock options, restricted stock shares, restricted stock units and performance award shares as of June 30, 2018 and 2017 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 Income —In addition to net losses, the comprehensive loss includes foreign currency translation adjustments and unrealized losses on investments. Accumulated other comprehensive income (loss) consisted of the following (net of tax):     Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Total accumulated other comprehensive income (loss) at beginning of period $ 112 $ (393) $ 34 $ (468)  Unrealized Losses on Investments  Balance at beginning of period $ (14) $ (19) $ (6) $ (21)  Other comprehensive income (loss) before reclassifications 1 4 (7) 6  Balance at end of period $ (13) $ (15) $ (13) $ (15)  Foreign Currency Translation Adjustment  Balance at beginning of period $ 126 $ (374) $ 40 $ (447)  Other comprehensive (loss) income before reclassifications (349) 373 (181) 425  Amounts reclassified from accumulated other comprehensive income (loss) to other income (loss) 138 (31) 56 (10)  Balance at end of period $ (85) $ (32) $ (85) $ (32)  Total accumulated other comprehensive loss at end of period $ (98) $ (47) $ (98) $ (47)  Research and Development Costs —Research and development costs are expensed as incurred. These costs include compensation and other costs associated with the development of and research related to new and existing products or concepts, preclinical studies, clinical trials and regulatory affairs. Advertising Costs — The Company expenses advertising costs as incurred. Advertising costs were not significant during the three and six months ended June 30, 2018 and 2017 . Share-Based Compensation —The Company records share-based compensation for all employee share-based payment awards, including stock options, restricted stock, restricted stock units, performance shares and stock purchases related to an employee stock purchase plan, based on estimated fair values. The value of the portion of an award that is ultimately expected to vest, net of estimated forfeitures, is recognized as expense over the service period in the Company’s Condensed Consolidated Statements of Operations and Comprehensive Loss. The Company estimates forfeitures at the time of grant and adjusts them in subsequent periods if actual forfeitures differ from those estimates. The Company recognized share-based compensation expense of $3,534 and $3,697 for the three months ended June 30, 2018 and 2017 and $7,424 and $7,325 for the six months ended June 30, 2018 and 2017. 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 is affected by the Company’s stock price, as well as subjective variables including, but 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 Company estimates the fair value of restricted stock, restricted stock units and performance shares based upon the grant date closing market price of the Company’s common stock. The Company also has an employee stock purchase plan (ESPP) which is available to all eligible employees as defined by the plan document. Under the ESPP, shares of the Company’s common stock may be purchased at a discount. At the beginning of each purchase period, the Company estimates the number of shares to be purchased in the period and the fair value of the shares based upon the Company’s stock price on the first day of the purchase period using the Black-Scholes model. Estimated compensation expense is recorded during the purchase period and is trued up to actual at the time of stock purchase. Use of Estimates —The preparation of the financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingencies in the financial statements. Actual results could differ from those estimates.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2018
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncements	2. RECENT ACCOUNTING PRONOUNCEMENTS In February 2016 , the FASB issued ASU 2016-02, “Leases” (ASU 2016-02) , codified as ASC 842, which requires lessees to record most leases onto their balance sheet but recognize expenses on their income statement in a manner similar to today’s accounting. The guidance is effective for interim and annual reporting periods beginning within 2019 . An entity is required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited . The Company intends to adopt ASU 2016-02 on the effective date of January 1, 2019 and is currently evaluating the provisions of ASU 2016-02 to determine the impact on its consolidated financial statements and related disclosures . In January 2017, the FASB issued ASU 2017-04, “ Intangibles - Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment ” (ASU 2017-04) . The guidance removes the requirement to perform a hypothetical purchase price allocation to measure goodwill impairment. Under ASU 2017-04, a goodwill impairment will be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The guidance becomes effective for annual reporting periods beginning after December 15, 2019 and interim periods within those fiscal years, with early adoption permitted, and applied prospectively. The Company is evaluating the provisions of ASU 2017-04 to determine the impact on its consolidated financial statements and related disclosures . In February 2018, the FASB issued ASU 2018-02, “Reclassification of Certain Tax Effects f rom Accumulated Other Comprehensive Income (AOCI)” (ASU 2018-02) to address industry concerns related to the application of ASC 740, “Income Taxes” to certain provisions of the new tax reform legislation. Upon adopting ASU 2018-02, an entity is required to disclose (1) its accounting policy related to releasing income tax effects from AOCI, (2) whether it has elected to reclassify, to retained earnings in the statement of stockholders’ equity, the stranded tax effects in AOCI related to the new tax reform legislation and (3) if it has elected to reclassify to retained earnings the stranded tax effects in AOCI related to the new tax reform legislation, what the reclassification encompasses. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. An entity will apply this guidance to each period in which the effect of the new tax reform legislation (or portion thereof) is recorded and may apply it either (1) retrospectively as of the date of enactment or (2) as of the beginning of the period of adoption. The Company has evaluated the impact of the provisions of ASU 2018-02 on its consolidated financial position, results of operations and related disclosures and determine d that the new guidance will not have a material impact on its financial reporting upon adoption . In March 2018, the FASB issued ASU 2018-05, “ Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118 ” (ASU 2018-05) to amend SEC paragraphs in ASC 740, “ Income Taxes, ” to reflect SAB 118 , which provides guidance for companies that are not able to complete their accounting for the income tax effects of the Tax Cuts and Jobs Act in the period of enactment. The Company is applying the guidance in SAB 118 when accounting for the enactment-date effects of the Act. See Note 9 for further discussion. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842, Leases” (ASU 2018-10). The amendments in this ASU address the rate implicit in the lease, impairment of the net investment in the lease, lessee reassessment of lease classification, lessor reassessment of lease term and purchase options, variable payments that depend on an index or rate and certain transition adjustments, among other things. The amendments have the same effective date as ASU 2016-02, which is effective for interim and annual reporting periods beginning within 2019 . The Company is evaluating the provisions of ASU 2018-10 to determine the impact on its consolidated financial statements and related disclosures. 

Fair Value

Fair Value	6 Months Ended
	Jun. 30, 2018
Fair Value [Abstract]
Fair Value	3. FAIR VALUE F air value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value maximize the use of observable inputs and minimize the use of unobservable inputs. The f air value hierarchy defines a three-level valuation hierarchy for classification and disclosure of fair value measurements as follows : · Level 1—Quoted prices in active markets for identical assets or liabilities. · 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. · 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. The Company classifies cash , investments in U.S. government securities , a ccounts receivable, short-term other assets, accounts payable and accrued liabilities as Level 1 within the fair value hierarchy. The carrying amounts of these assets and liabilities approximate their fair value due to their relatively short-term nature. Cash equivalents and investments in corporate bonds, commercial paper and asset-backed securities are classified as Level 2 within the fair value hierarchy. The fair value of fixed term d ebt is estimated by calculating the net present value of future debt payments at current market interest rates and is classified as Level 2. The book value of the Company’s fixed term debt approximates its fair value because the interest rate varies with market rates . 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 June 30, 2018 :      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 $ — $ 2,603 $ — $ 2,603  Commercial paper — 8,541 — 8,541  U.S. government securities 2,584 — — 2,584  Corporate bonds — 8,099 — 8,099  Asset-backed securities — 3,978 — 3,978  Total assets $ 2,584 $ 23,221 $ — $ 25,805  Liabilities:  Acquisition-related contingent consideration — — 31,182 31,182  Total liabilities $ — $ — $ 31,182 $ 31,182 There were no changes in the levels or methodology of measurement of financial assets and liabilities during the three and six months ended June 30, 2018 . 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 December 31, 2017 :      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 $ — $ 12,774 $ — $ 12,774  Commercial paper — 7,472 — 7,472  U.S. government agencies and securities 2,999 — — 2,999  Corporate bonds — 2,920 — 2,920  Total assets $ 2,999 $ 23,166 $ — $ 26,165  Liabilities:  Acquisition-related contingent consideration — — 37,098 37,098  Total liabilities $ — $ — $ 37,098 $ 37,098 Acquisition-Related Contingent Consideration. Contingent consideration arrangements under the nContact merger agreement obligate the Company to pay certain defined amounts to former shareholders of nContact if specified milestones are met related to trial enrollment, regulatory approval and revenue targets. The Company measures contingent consideration liabil ities using unobservable inputs by applying an income approach, such as the discounted cash flow technique or the probability-weighted scenario method. Various key assumptions, such as the probability of achievement of the agreed milestones, projected revenues from acquisitions and the discount rate, are used in the determination of fair value of contingent consideration arrangements and are not observable in the market, thus representing a Level 3 measurement within the fair value hierarchy. Subsequent revisions to key assumptions, which impact the estimated fair value of contingent consideration liabilities, are reflected in the Condensed Consolidated Statements of Operations and Comprehensive Loss. Acquisition-related contingent consideration is recorded in other noncurrent liabilities in the Condensed Consolidated Balance Sheets. The fair value of the nContact contingent consideration was remeasured as of June 30, 2018 , resulting in a decrease in fair value of $ 5,916. This decrease is primarily due to changes in estimates related to the timing of achievement of the regulatory milestone as a result of enrollment in the CONVERGE IDE clinical trial in 2018, a decrease in forecasted revenues under the commercial milestone payment a nd a higher discount rate, reflecting increases in market interest rates and changes to the Company’s debt structure . The adjustment to fair value is recorded in selling, general and administrative expenses in the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. The following table represents the Company’s Level 3 fair value measurements using significant other unobservable inputs for acquisition-related contingent consideration:        Six Months Ended Twelve Months Ended  June 30, December 31, 2017  Beginning Balance $ 37,098 $ 41,176  Amounts acquired — —  Changes in fair value included in earnings (5,916) (4,078)  Ending Balance $ 31,182 $ 37,098 

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2018
Intangible Assets [Abstract]
Intangible Assets	4. INTANGIBLE ASSETS The following table provides a summary of the Company’s intangible assets:       June 30, 2018 December 31, 2017  Estimated Useful Life Cost Accumulated Amortization Cost Accumulated Amortization  Fusion technology 10 years $ 9,242 $ 4,159 $ 9,242 $ 3,697  SUBTLE access technology 5 years 2,179 1,203 2,179 981  IPR&D 44,021 — 44,021 —  Total $ 55,442 $ 5,362 $ 55,442 $ 4,678 Amortization expense of intangible assets with definite lives, which excludes IPR&D, was $342 for both the three months ended June 30, 2018 and 2017 and $684 for both the six months ended June 30, 2018 and 2017 . A mortization expense of intangible assets with definite lives is projected as follows:      2018 $ 683 July 1, 2018 through December 31, 2018  2019 1,367  2020 1,235  2021 924  2022 925  2023 and thereafter 925  Total $ 6,059

Accrued Liabilities

Accrued Liabilities	6 Months Ended
	Jun. 30, 2018
Accrued Liabilities [Abstract]
Accrued Liabilities	5. ACCRUED LIABILITIES Accrued liabilities consisted of the following:      June 30, December 31,  2018 2017  Accrued commissions $ 5,416 $ 6,964  Accrued payroll and employee-related expenses 4,370 4,097  Accrued bonus 4,163 4,726  Sales returns and allowances 1,319 1,169  Other accrued liabilities 701 695  Accrued royalties 669 626  Accrued taxes 523 634  Total $ 17,161 $ 18,911

Indebtedness

Indebtedness	6 Months Ended
	Jun. 30, 2018
Indebtedness [Abstract]
Indebtedness	6. INDEBTEDNESS Credit Facility. The Company has a Loan and Security Agreement (Loan Agreement) with Silicon Valley Bank (SVB). The Loan Agreement, as amended and restated effective February 23, 2018 , includes a $40,000 term loan an d a $20,000 revolving line of credit , with an option to increase the revolving line of credit by up to an additional $20,000 . The term loan and revolving line of credit each have a five -year term , maturing or expiring , as applicable, in February 2023 . Principal payments o f the term loan are to be made ratably commencing eighteen months after the inception of the loan (September 2019) through the loan’s maturity date. If the Company meets certain conditions, as specified by the Loan A greement, the commencement of term loan principal payments may be deferred by an additional six months. The term loan accrues interest at the greater of the Prime Rate plus 3.75%, or 8.25%, a nd is subject to an additional 3.5% fee on the original $ 40 ,000 term loan principal payable at maturity or upon acceleration or prepayment of the term loan. The Company is accruing the 3.5 % fee over the term of the Loan Agreement. As of June 30, 2018 , the Company accrued $93 of this fee , reflected in the outstanding loan balance in the Condensed Consolidated Balance Sheets. The refinancing was treated as a debt modification. F inancing costs related to the term loan of $744 are net ted against the outstanding loan balance in the Condensed Consolidated Balance Sheets and amortized ratably over the term of the Loan Agreement. The revolving line of credit is subject to an annual facility fee of 0.33% of the revolving line of credit, and any borrowings bear interest at the greater of the Prime Rate or 4.50% . Borrowing availability under the revolving credit facility is based on the lesser of $ 20 ,000 or a borrowing base calculation as defined by the Loan Agreement. As of June 30, 2018 , the Company had no borrowings under the revolving credit facility and had borrowing availability of $18,750 . Financing costs related to the revolving line of credit are included in other assets in the Condensed Consolidated Balance Sheets and amortized ratably over the twelve-month period of the annual fee . The Loan Agreement contains prepayment and early termination fees and establishes a financial covenant related to sales growth, along with other customary terms and conditions. Specified assets have been pledged as collateral. Capital Lease Obligations. As of June 30, 2018 , the Company had capital leases for its corporate headquarters building and certain equipment that expire at various terms through 2030 . C apital lease assets are depreciated over their estimated useful lives. As of June 30, 2018 , the cost of the leased assets, both building and equipment, was $14,462 , and related accumul ated amortization was $2,699 . In connection with the terms of the Company’s corporate headquarters lease, a letter of credit in the amount of $1,250 was issued to the building lessor in October 2015. The letter of credit is renewed annually and remain ed outstanding as of June 30, 2018 . Future maturities of long-term debt , including the term loan fee payable at maturity, and capital lease obligations are projected as follows:     2018 $ 736 July 1, 2018 through December 31, 2018  2019 5,303  2020 12,943  2021 12,947  2022 12,968  2023 and thereafter 16,260  Total payments $ 61,157  Imputed interest (6,676)  Net long-term debt and capital lease obligations, of which $589 is current and $53,892 is noncurrent $ 54,481  

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies [Abstract]
Commitments and Contingencies	7. COMMITMENTS AND CONTINGENCIES Lease Commitments. The Company leases certain office and warehouse facilities under noncancelable operating leases with various terms that expire through 2022 . Royalty Agreements. The Company has certain royalty agreements in place with terms that include payment of royalties of 3% to 5% of specified product sales. The royalty agreements have effective dates as early as 2003 and terms ranging from eighteen to at least twenty years, unless terminated earlier. Royalty expense of $695 and $602 is included in cost of rev enue for the three months ended June 30, 2018 and 2017 . Royalty expense of $1,367 and $1,136 is included in cost of revenue for the six months ended June 30, 2018 and 2017 . Purchase Agreements. The Company enters into standard purchase agreements with various suppliers in the ordinary course of business. Outstanding commitments outside of the ordinary course of business were not significant at June 30, 2018 . Legal. The Company may, from time to time, become a party to legal proceedings and receive inquiries from regulators . Such matters are subject to many uncertainties and to outcomes of which the financial impacts are not predictable with assurance and that may not be known for extended periods of time. When the Company has assessed that a loss is probable and an amount can be reasonably estimated, it records a liability in the Condensed Consolidated Financial Statements. Costs associated with legal proceedings could have a material adverse effect on the Company’s future consolidated results of operations, financial position, or cash flows. The Company received a Civil Investigative Demand (CID) from the U.S. Department of Justice in December 2017 stating that it is investigating the Company to determine whether the Company has violated the False Claims Act, relating to the promotion of certain medical devices related to the treatment of atrial fibrillation for off-label use and submitted or caused to be submitted false claims to certain federal and state health care programs for medically unnecessary healthcare services related to the treatment of atrial fibrillation. The CID covers the period from January 2010 to December 2017 and requires the production of documents and answers to written interrogatories. The Company had no knowledge of the investigation prior to receipt of the CID. The Company maintains rigorous policies and procedures to promote compliance with the False Claims Act and other applicable regulatory requirements , and it is working with the U.S. Department of Justice to promptly respond to the CID. However, the Company cannot predict when the investigation will be resolved, the outcome of the investigation or its potential impact on the Company. The Company acquired nContact Surgical, Inc. pursuant to a merger agreement dated October 4, 2015. The merger agreement provides for contingent consideration or "earnout" to be paid upon attaining specified regulatory approvals and clinical and revenue milestones. The merger agreement’s earnout provisions require the Company to deliver periodic earnout reports to a designated representative of former nContact stockholders. In response to the report delivered in February 2018, the Company received a letter from the representative on March 16, 2018. The letter purports to serve as an “earnout objection statement” (as that term is defined in the merger agreement) and claims that for purposes of determining the commercial milestone payment, the Company should be including revenues of certain additional items and products that the Company has not previously included in its earnout statements . The Company has dispute d the basis of the representative’s claims , and ha s correspond ed with the representative regarding the earnout objection statement.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2018
Revenue [Abstract]
Revenue	8. REVENUE The Company adopted FASB ASC 606, “Revenue from Contracts with Customers” (ASC 606) using the modified retrospective method effective January 1, 2018. The adoption of ASC 606 did not have a material impact on the amount and timing of revenue recognized in the Condensed C onsolidated Fi nancial S tatements. Revenue is generated primarily from the sale of disposable surgical devices. The Company recognizes revenue in an amount that reflects the consideration the Company expects to be entitled to in exchange for those devices when control of promised devices is transferred to customers. At contract inception, the Company assesses the products promised in its contracts with customers and identifies a performance obligation for each promise to transfer to the customer a product that is distinct. The Company’s disposable surgical devices are distinct and represent performance obligations. These performance obligations are satisfied and revenue is recognized at a point in time upon shipment or delivery of products. Sales of devices are categorized as follows: open-heart ablation, minimally invasive ablation (MIS), appendage management and valve tools. Shipping and handling activities performed after control over products transfers to customers are considered activities to fulfill the promise to transfer the products rather than as separate promises to customers. Products are sold primarily through a direct sales force and through distributors in select international markets. 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, with limited exceptions. The Company does not maintain any post-shipping obligations to customers. No installation, calibration or testing of products is performed by the Company subsequent to shipment in order to render products operational. Significant judgments and estimates involved in the Company’s recognition of revenue include the determination of the timing of transfer of co ntrol of products to customers and the estimation of a provision for returns. The Company considers the following indicators when determining when the control of products transfers to customers: (i) the Company has a right to payment in accordance with the shipping terms set forth in its contracts with customers; (ii) customers have legal title to products in accordance with shipping terms; (iii) the Company transfers physical possession of products either when the Company presents the products to a third party carrier for delivery to a customer (FOB shipping point) or when a customer receives the delivered goods (FOB destination); (iv) customers have the significant risks and rewards of ownership of products; and (v) customers have accepted products in connection with contractual shipping terms. In the normal course of business, the Company does not accept product returns unless a product is defective as manufactured. The Company establishes estimated provisions for returns based on historical experience. The Company does not provide customers with the right to a refund. The Company expects to be entitled to the total consideration for the products ordered by customers as product pricing is fixed according to the terms of customer contracts and payment terms are short. Payment terms fall within the one-year guidance for the practical expedient which allows the Company to forgo adjustment of the promised amount of consideration for the effects of a significant financing component. The Company excludes taxes assessed by governmental authorities on revenue-producing transactions from the measurement of the transaction price. Costs associated with product sales include commissions and royalties. Considering that product sales are performance obligations in contracts that are satisfied at a point in time, commission expense associated with product sales and royalties paid based on sales of certain products is incurred at that point in time rather than over time. Therefore, the Company applies the practical expedient and recognizes commissions and royalties as expense when incurred because the expense is incurred at a point in time and the amortization period is less than one year. Commissions are recorded as selling expense and royalties are recorded as cost of rev enue in the Condensed Consolidated Statements of Operations and Comprehensive Loss . See Note 11 for disaggregated revenue by geographic area and by product category. 

Income Tax Provision

Income Tax Provision	6 Months Ended
	Jun. 30, 2018
Income Tax Provision [Abstract]
Income Tax Provision	9 . INCOME TAX PROVISION The Company files federal, state, and foreign income tax returns in jurisdictions with varying statutes of limitations . The Company uses the asset and liability method to determine its provision for income taxes. The Company’s provision for income taxes in interim periods is computed by applying its estimated annual effective rate against its pre-tax results for the period. N on-recurring items are recorded during the period in which they occur. The effective tax rate for the three months ended June 30, 2018 and 2017 was (16.64%) and (0.25%) . The effective tax rate for the six months ended June 30, 2018 and 2017 was (0.92%) and (0.23%) . The Tax Cuts and Jobs Act (TCJA) was enacted o n December 22, 2017 . The TCJA reduces the United States federal corporate income tax rate from 35% to 21% , along with other changes to tax law . As a result of the Company’s valuation allowance on its net U . S . deferred tax assets, the TCJA did not have an impact on the effective tax rate for the three and six months ended June 30, 2018 as compared to June 30, 2017 . The Company is applying the guidance in Staff Accounting Bulletin No. 118 , “Income Tax Accounting Implications of the Tax Cut and Jobs Act” (SAB 118) when accounting for the enactment-date effects of the TCJA. As of June 30, 2018, the Company has not adjusted the provisional amounts recognized as of December 31, 2017. The provisional amounts recorded may be affected as the Company completes additional analysis of the tax law provisions. These changes are not anticipated to be material to the Company’s Condensed Consolidated Financial Statements as a result of a full valuation allowance against the Company’s net U.S. deferred tax assets. Federal, state and local tax returns of the Company are routinely subject to review by various taxing authorities. The Company has not accrued 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 income tax expense in the Condensed Consolidated Statements of Operations and Comprehensive Loss and within the related tax liability in the Condensed Consolidated Balance Sheets. 

Equity Compensation Plans

Equity Compensation Plans	6 Months Ended
	Jun. 30, 2018
Equity Compensation Plans [Abstract]
Equity Compensation Plans	10 . EQUITY COMPENSATION PLANS The Company has two share-based incentive plans: the 2014 Stock Incentive Plan (2014 Plan) and the 20 1 8 Employee Stock Purchase Plan (ESPP). Stock Incentive Plan Under the 2014 Plan, the Board of Directors may grant incentive stock options to employees and may grant nonstatutory stock options, restricted stock , restricted stock units, performance shares or stock appreciation rights to employees, directors and consultants. The administrator (the Compensation Committee of the Board of Directors) has the authority to determine the terms of any awards, including the number of shares subject to each award, the exercisability of the awards and the form of consideration. As of June 30, 2018 , 10,249 shares of common stock had been reserved for issuance under the 2014 Plan , and 513 shares were available for future grants . An additional 850 shares were approved by stockholders at the Company’s 2018 Annual Meeting of Stockholders in May 2018 which will be registered during the third quarter of 2018. Effective March 1, 2018, the Compensation Committee of the Board approved the grant o f performance share awards ( 2018 PSAs) to the Company’s named executive officers and certain other executive employees pursuant to the Company’s 2014 Stock Incentive Plan. The form of award agreement for the 2018 PSAs ( 2018 PSA Grant Form) provides, among other things, that (i) each 2018 PSA that vests represents the right to receive one share of the Company’s common stock; (ii) the 2018 PSAs vest based on the Company achieving specified performance measurements over a performance period of three years, beginning January 1, 2018; (iii) the performance measurements include revenue CAGR as defined in the 2018 PSA Grant Form; (iv) threshold, target and maximum payout opportunities established for the 2018 PSAs will be used to calculate the number of shares that will be issuable when the award vests, which may range from 0% to 200% of the target amount; (v) any 2018 PSAs that are earned are scheduled to vest and be settled in shares of the Company’s common stock at the end of the performance period; and (vi) all or a portion of the 2018 PSAs may vest following a change of control or a termination of service by reason of death or disability (each as described in greater detail in the 2018 PSA Grant Form). With respect to the 2018 PSAs, the number of shares that vest and are issued to the recipient is based upon the Company’s performance as measured against the specified targets at the end of the three-year performance period as determined by the Compensation Committee of the Board. The Company estimated the fair value of the 2018 PSAs based on its closing stock price on the grant date and will adjust compensation expense over the performance period based on its estimate of performance target achievement. Stock o ptions granted prior to 2018 under the 2014 Plan generally expire ten years from the date of grant and 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 prior to 2018 generally vest between one and four years from the date of grant . Beginning in 2018, stock options granted generally vest in one -third increments on the first, second and third anniversaries of the grant date, and restricted stock awards generally vest on the grant date anniversaries between one and three years from the date of grant. Restricted stock units vest in one -third increments on the first, second and third anniversaries of the grant date. Employee Stock Purchase Plan The ESPP is available to eligible employees as defined in the plan document. Under the ESPP, shares of the Company’s common stock may be purchased at a discount ( 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 a value of more than $25 of the Company’s common stock in a cale ndar year and may not purchase more than 3 shares during an offering period. The ESPP was approved by stockholders at the Company’s 2018 Annual Meeting of Stockholders in May 2018, resulting in an increase of 500 shares available for sale under the ESPP which will be registered during the third quarter of 2018. A s of June 30, 2018 , there were 136 shares available for future issuance under the ESPP. Expense Information Under FASB ASC 718 The following table summarizes the allocation of share-based compensation expense :      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Cost of revenue $ 239 $ 138 $ 476 $ 269  Research and development expenses 361 502 952 1,003  Selling, general and administrative expenses 2,934 3,057 5,996 6,053  Total $ 3,534 $ 3,697 $ 7,424 $ 7,325

Segment and Geographic Informat

Segment and Geographic Information	6 Months Ended
	Jun. 30, 2018
Segment and Geographic Information [Abstract]
Segment and Geographic Information	1 1 . SEGMENT AND GEOGRAPHIC INFORMATION 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 globally. Management considers all such sales to be part of a single operating segment. Revenue attributed to geographic areas, based on the location of customers, was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  United States $ 40,834 $ 35,534 $ 79,270 $ 68,802  Europe 6,694 5,688 12,565 10,877  Asia 4,049 3,785 6,488 6,436  Other international 225 224 473 389  Total international 10,968 9,697 19,526 17,702  Total revenue $ 51,802 $ 45,231 $ 98,796 $ 86,504  United States revenue by product type was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Open-heart ablation $ 18,073 $ 16,790 $ 35,652 $ 32,495  Minimally invasive ablation 9,114 8,725 17,727 17,007  Appendage management 13,101 9,463 24,898 18,165  Total ablation and appendage management 40,288 34,978 78,277 67,667  Valve tools 546 556 993 1,135  Total United States $ 40,834 $ 35,534 $ 79,270 $ 68,802  International revenue by product type was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Open-heart ablation $ 5,836 $ 5,674 $ 10,745 $ 10,264  Minimally invasive ablation 2,660 2,135 4,452 4,093  Appendage management 2,424 1,777 4,222 3,172  Total ablation and appendage management 10,920 9,586 19,419 17,529  Valve tools 48 111 107 173  Total international $ 10,968 $ 9,697 $ 19,526 $ 17,702 The Company’s long-lived assets are located primarily in the United States, except for $1,006 as of June 30, 2018 and $957 as of December 31, 201 7 , which are located primarily in Europe.

Description of Business and S17

Description of Business and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Description of Business and Summary of Significant Accounting Policies [Abstract]
Nature of the Business	Nature of the Business —The “Company” consists of AtriCure, Inc. and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The Company is a leading innovator in treatments for atrial fibrillation (Afib) and left atrial appendage (LAA) management, and sells its products to medical centers globally through its direct sales force and distributors.
Basis of Presentation	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 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 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 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, 2017 filed with the SEC.
Cash Equivalents	Cash Equivalents —The Company considers highly liquid investments with maturities of three months or less at the date of purchase as cash equivalents in the accompanying Condensed Consolidated Financial Statements.
Investments	Investments —The Company invests primarily in U.S. Government securities, corporate bonds, commercial paper and asset-backed securities and 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. Gains and losses are recognized using the specific identification method when securities are sold and are included in interest income or expense in the Condensed Consolidated Statements of Operations and Comprehensive Loss.
Revenue Recognition	Revenue Recognition— The Company recognizes revenue when control of promised goods is transferred to customers in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods. This generally occurs upon shipment of goods to customers. See Note 8 for further discussion on revenue.
Sales Returns and Allowances	Sales Returns and Allowances —The Company maintains a provision for potential returns of defective or damaged products and products shipped in error and invoice adjustments. The Company adjusts the provision through consideration of a combination of specific identification and historical experience. 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	Allowance for Doubtful Accounts Receivable —The Company evaluates the collectability of accounts receivable to determine the appropriate allowance for doubtful accounts considering the aging of accounts, historical credit losses, customer-specific information and other relevant factors. Increases to the allowance result in an increase in selling, general and administrative expenses. The Company 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 —Inventories are stated at the lower of cost or net realizable value based on the first-in, first-out cost method (FIFO). The Company’s industry is characterized by rapid product development and frequent new product introductions. Uncertain timing of regulatory approval, variability in product launch strategies and variation in product use cause the Company to maintain reserves for excess, obsolete and expired products. Increases to inventory reserves result in an increase in cost of revenue. Inventories are written off against reserves when they are physically disposed. Inventories consist of the following:      June 30, December 31,  2018 2017  Raw materials $ 8,729 $ 7,755  Work in process 1,549 1,299  Finished goods 11,404 13,397  Inventories $ 21,682 $ 22,451 
Property and Equipment	Property and Equipment —Property and equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of assets. The estimated useful life by major asset category is the following:      Estimated Useful Life  Generators and related equipment 1 - 3 years  Building under capital lease 15 years  Computers, software and office equipment 3 years  Machinery and equipment 3 - 7 years  Furniture and fixtures 3 - 7 years  Leasehold improvements 5 - 15 years  Equipment under capital leases 3 - 5 years The Company reassesses the useful lives of property and equipment at least annually and retires assets if they are no longer in service. Maintenance and repair costs are expensed as incurred. The Company’s radiofrequency (RF) and cryo generators are generally placed with customers that use the Company’s disposable products. The estimated useful lives of generators are based on anticipated usage by customers and may change in future periods with changes in usage or introduction of new technologies. Depreciation related to generators and related equipment, which is recorded in cost of revenue in the Condensed Consolidated Statements of Operations and Comprehensive Loss, was $814 and $909 for the three months ended June 30, 2018 and 2017 and $1,641 and $1,825 for the six months ended June 30, 2018 and 2017 . As of June 30, 2018 and December 31, 2017 , the net carrying value of generators and related equipment included in net property and equipment in the Condensed Consolidated Balance Sheets was $4,717 and $4,656 . The Company reviews property and equipment for impairment at least annually using its best estimates based on reasonable and supportable assumptions and expected future cash flows. Property and equipment impairments recorded by the Company have not been significant.
Intangible Assets	Intangible Assets —Intangible assets with determinable useful lives are amortized on a straight-line basis over the estimated periods benefited. Intangible assets include In-Process Research and Development (IPR&D), which represents the value of technology acquired in business combinations that has not yet reached technological feasibility. The primary basis for determining technological feasibility is obtaining specific regulatory approval. IPR&D is accounted for as an indefinite-lived intangible asset until completion or abandonment of the IPR&D project. Upon completion of the development project, IPR&D will be amortized over its estimated useful life. If the IPR&D project is abandoned, the IPR&D would be written off. IPR&D represents an estimate of the fair value of the pre-market approval (PMA) that may result from the CONVERGE IDE clinical trial. The Company reviews intangible assets for impairment at least annually using its best estimates based on reasonable and supportable assumptions and projections. The Company has historically tested IPR&D for impairment annually on November 30.
Goodwill	 Goodwill— Goodwill represents the excess of purchase price over the fair value of the net assets acquired in business combinations. The Company has historically tested 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’s consolidated operations.
Other Noncurrent Liabilities	Other Noncurrent Liabilities— Other noncurrent liabilities consist of acquisition-related contingent consideration and other contractual obligations. Although the Company expects to settle a portion of the contingent consideration liability in 2018, the balance is included in noncurrent liabilities as such settlement is both required and expected to be made in shares of the Company’s common stock pursuant to the nContact Surgical, Inc. (nContact) merger agreement.
Other Income (Expense)	Other Income (Expense) — Other income (expense) consists primarily of foreign currency transaction gains and losses generated by settlements of intercompany balances denominated in Euros and customer invoicing in British Pounds.
Taxes	Taxes —Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred income 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 income 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 income tax assets requires significant estimates and judgments about future operating results. Deferred income tax assets are reduced by valuation allowances if, based on the consideration of all available evidence, it is more-likely-than-not that the deferred income tax asset will not be realized. Significant weight is given to evidence that can be objectively verified. The Company evaluates deferred income tax assets on an annual basis to determine if valuation allowances are required. Deferred income 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 income 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 the need for a valuation allowance, the existence of cumulative losses in recent years is significant 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 substantially all net deferred income tax assets as it is more-likely-than-not that the benefit of the deferred income tax assets will not be recognized in future periods.
Net Loss Per Share	Net Loss Per Share —Basic and diluted net loss per share is computed 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 4,063 and 4,349 stock options, restricted stock shares, restricted stock units and performance award shares as of June 30, 2018 and 2017 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 Income	Comprehensive Loss and Accumulated Other Comprehensive Income —In addition to net losses, the comprehensive loss includes foreign currency translation adjustments and unrealized losses on investments. Accumulated other comprehensive income (loss) consisted of the following (net of tax):     Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Total accumulated other comprehensive income (loss) at beginning of period $ 112 $ (393) $ 34 $ (468)  Unrealized Losses on Investments  Balance at beginning of period $ (14) $ (19) $ (6) $ (21)  Other comprehensive income (loss) before reclassifications 1 4 (7) 6  Balance at end of period $ (13) $ (15) $ (13) $ (15)  Foreign Currency Translation Adjustment  Balance at beginning of period $ 126 $ (374) $ 40 $ (447)  Other comprehensive (loss) income before reclassifications (349) 373 (181) 425  Amounts reclassified from accumulated other comprehensive income (loss) to other income (loss) 138 (31) 56 (10)  Balance at end of period $ (85) $ (32) $ (85) $ (32)  Total accumulated other comprehensive loss at end of period $ (98) $ (47) $ (98) $ (47) 
Research and Development Costs	Research and Development Costs —Research and development costs are expensed as incurred. These costs include compensation and other costs associated with the development of and research related to new and existing products or concepts, preclinical studies, clinical trials and regulatory affairs.
Advertising Costs	Advertising Costs — The Company expenses advertising costs as incurred. Advertising costs were not significant during the three and six months ended June 30, 2018 and 2017 .
Share-Based Compensation	Share-Based Compensation —The Company records share-based compensation for all employee share-based payment awards, including stock options, restricted stock, restricted stock units, performance shares and stock purchases related to an employee stock purchase plan, based on estimated fair values. The value of the portion of an award that is ultimately expected to vest, net of estimated forfeitures, is recognized as expense over the service period in the Company’s Condensed Consolidated Statements of Operations and Comprehensive Loss. The Company estimates forfeitures at the time of grant and adjusts them in subsequent periods if actual forfeitures differ from those estimates. The Company recognized share-based compensation expense of $3,534 and $3,697 for the three months ended June 30, 2018 and 2017 and $7,424 and $7,325 for the six months ended June 30, 2018 and 2017. 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 is affected by the Company’s stock price, as well as subjective variables including, but 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 Company estimates the fair value of restricted stock, restricted stock units and performance shares based upon the grant date closing market price of the Company’s common stock. The Company also has an employee stock purchase plan (ESPP) which is available to all eligible employees as defined by the plan document. Under the ESPP, shares of the Company’s common stock may be purchased at a discount. At the beginning of each purchase period, the Company estimates the number of shares to be purchased in the period and the fair value of the shares based upon the Company’s stock price on the first day of the purchase period using the Black-Scholes model. Estimated compensation expense is recorded during the purchase period and is trued up to actual at the time of stock purchase.
Use of Estimates	 Use of Estimates —The preparation of the financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingencies in the financial statements. Actual results could differ from those estimates.

Description of Business and S18

Description of Business and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Description of Business and Summary of Significant Accounting Policies [Abstract]
Summary Of Inventories	Inventories consist of the following:      June 30, December 31,  2018 2017  Raw materials $ 8,729 $ 7,755  Work in process 1,549 1,299  Finished goods 11,404 13,397  Inventories $ 21,682 $ 22,451 
Summary of Property and Equipment	   Estimated Useful Life  Generators and related equipment 1 - 3 years  Building under capital lease 15 years  Computers, software and office equipment 3 years  Machinery and equipment 3 - 7 years  Furniture and fixtures 3 - 7 years  Leasehold improvements 5 - 15 years  Equipment under capital leases 3 - 5 years 
Accumulated Other Comprehensive Income (Loss)	 Accumulated other comprehensive income (loss) consisted of the following (net of tax):     Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Total accumulated other comprehensive income (loss) at beginning of period $ 112 $ (393) $ 34 $ (468)  Unrealized Losses on Investments  Balance at beginning of period $ (14) $ (19) $ (6) $ (21)  Other comprehensive income (loss) before reclassifications 1 4 (7) 6  Balance at end of period $ (13) $ (15) $ (13) $ (15)  Foreign Currency Translation Adjustment  Balance at beginning of period $ 126 $ (374) $ 40 $ (447)  Other comprehensive (loss) income before reclassifications (349) 373 (181) 425  Amounts reclassified from accumulated other comprehensive income (loss) to other income (loss) 138 (31) 56 (10)  Balance at end of period $ (85) $ (32) $ (85) $ (32)  Total accumulated other comprehensive loss at end of period $ (98) $ (47) $ (98) $ (47) 

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	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 June 30, 2018 :      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 $ — $ 2,603 $ — $ 2,603  Commercial paper — 8,541 — 8,541  U.S. government securities 2,584 — — 2,584  Corporate bonds — 8,099 — 8,099  Asset-backed securities — 3,978 — 3,978  Total assets $ 2,584 $ 23,221 $ — $ 25,805  Liabilities:  Acquisition-related contingent consideration — — 31,182 31,182  Total liabilities $ — $ — $ 31,182 $ 31,182 There were no changes in the levels or methodology of measurement of financial assets and liabilities during the three and six months ended June 30, 2018 . 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 December 31, 2017 :      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 $ — $ 12,774 $ — $ 12,774  Commercial paper — 7,472 — 7,472  U.S. government agencies and securities 2,999 — — 2,999  Corporate bonds — 2,920 — 2,920  Total assets $ 2,999 $ 23,166 $ — $ 26,165  Liabilities:  Acquisition-related contingent consideration — — 37,098 37,098  Total liabilities $ — $ — $ 37,098 $ 37,098 
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:        Six Months Ended Twelve Months Ended  June 30, December 31, 2017  Beginning Balance $ 37,098 $ 41,176  Amounts acquired — —  Changes in fair value included in earnings (5,916) (4,078)  Ending Balance $ 31,182 $ 37,098 

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2018
Intangible Assets [Abstract]
Company's Intangible Assets	The following table provides a summary of the Company’s intangible assets:       June 30, 2018 December 31, 2017  Estimated Useful Life Cost Accumulated Amortization Cost Accumulated Amortization  Fusion technology 10 years $ 9,242 $ 4,159 $ 9,242 $ 3,697  SUBTLE access technology 5 years 2,179 1,203 2,179 981  IPR&D 44,021 — 44,021 —  Total $ 55,442 $ 5,362 $ 55,442 $ 4,678 
Future Amortization Expense Related to Intangible Assets with Definite Lives	A mortization expense of intangible assets with definite lives is projected as follows:      2018 $ 683 July 1, 2018 through December 31, 2018  2019 1,367  2020 1,235  2021 924  2022 925  2023 and thereafter 925  Total $ 6,059 

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
Accrued Liabilities [Abstract]
Accrued Liabilities	Accrued liabilities consisted of the following:      June 30, December 31,  2018 2017  Accrued commissions $ 5,416 $ 6,964  Accrued payroll and employee-related expenses 4,370 4,097  Accrued bonus 4,163 4,726  Sales returns and allowances 1,319 1,169  Other accrued liabilities 701 695  Accrued royalties 669 626  Accrued taxes 523 634  Total $ 17,161 $ 18,911 

Indebtedness (Tables)

Indebtedness (Tables)	6 Months Ended
	Jun. 30, 2018
Indebtedness [Abstract]
Future Maturities On Debt And Capital Lease Obligations	   2018 $ 736 July 1, 2018 through December 31, 2018  2019 5,303  2020 12,943  2021 12,947  2022 12,968  2023 and thereafter 16,260  Total payments $ 61,157  Imputed interest (6,676)  Net long-term debt and capital lease obligations, of which $589 is current and $53,892 is noncurrent $ 54,481 

Equity Compensation Plans (Tabl

Equity Compensation Plans (Tables)	6 Months Ended
	Jun. 30, 2018
Equity Compensation Plans [Abstract]
Share-Based Compensation Expense Related to Employee Share-Based Compensation	The following table summarizes the allocation of share-based compensation expense :      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Cost of revenue $ 239 $ 138 $ 476 $ 269  Research and development expenses 361 502 952 1,003  Selling, general and administrative expenses 2,934 3,057 5,996 6,053  Total $ 3,534 $ 3,697 $ 7,424 $ 7,325 

Segment and Geographic Inform24

Segment and Geographic Information (Tables)	6 Months Ended
	Jun. 30, 2018
Segment and Geographic Information [Abstract]
Revenue by Geographic Area	Revenue attributed to geographic areas, based on the location of customers, was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  United States $ 40,834 $ 35,534 $ 79,270 $ 68,802  Europe 6,694 5,688 12,565 10,877  Asia 4,049 3,785 6,488 6,436  Other international 225 224 473 389  Total international 10,968 9,697 19,526 17,702  Total revenue $ 51,802 $ 45,231 $ 98,796 $ 86,504 
Revenue by Product Type	United States revenue by product type was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Open-heart ablation $ 18,073 $ 16,790 $ 35,652 $ 32,495  Minimally invasive ablation 9,114 8,725 17,727 17,007  Appendage management 13,101 9,463 24,898 18,165  Total ablation and appendage management 40,288 34,978 78,277 67,667  Valve tools 546 556 993 1,135  Total United States $ 40,834 $ 35,534 $ 79,270 $ 68,802  International revenue by product type was as follows:      Three Months Ended Six Months Ended  June 30, June 30,  2018 2017 2018 2017  Open-heart ablation $ 5,836 $ 5,674 $ 10,745 $ 10,264  Minimally invasive ablation 2,660 2,135 4,452 4,093  Appendage management 2,424 1,777 4,222 3,172  Total ablation and appendage management 10,920 9,586 19,419 17,529  Valve tools 48 111 107 173  Total international $ 10,968 $ 9,697 $ 19,526 $ 17,702 

Description of Business and S25

Description of Business and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Description Of Business And Significant Accounting Policies [Line Items]
Depreciation			$ 3,719	$ 3,906
Net carrying amount of loaned equipment	$ 28,126		$ 28,126		$ 28,749
Options, restricted stock and performance based shares excluded from calculation of net loss per share			4,063	4,349
Share-based compensation expense recognized	3,534	$ 3,697	$ 7,424	$ 7,325
Generators And Related Equipment [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Depreciation	814	$ 909	1,641	$ 1,825
Carrying Amount of Loaned Equipment [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Net carrying amount of loaned equipment	$ 4,717		$ 4,717		$ 4,656
Short-term Debt [Member]
Description Of Business And Significant Accounting Policies [Line Items]
Maturity period of short term investment			1 year

Description of Business and S26

Description of Business and Summary of Significant Accounting Policies (Summary Of Inventories) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Description of Business and Summary of Significant Accounting Policies [Abstract]
Raw materials	$ 8,729	$ 7,755
Work in process	1,549	1,299
Finished goods	11,404	13,397
Inventories	$ 21,682	$ 22,451

Description of Business and S27

Description of Business and Summary of Significant Accounting Policies (Summary Of Property And Equipment) (Details)	6 Months Ended
	Jun. 30, 2018
Building under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Computers, Software and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Minimum [Member] | Generator and Related Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	1 year
Minimum [Member] | Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Minimum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Minimum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Minimum [Member] | Equipment under Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Maximum [Member] | Generator and Related Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Maximum [Member] | Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Maximum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Maximum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Maximum [Member] | Equipment under Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years

Description of Business and S28

Description of Business and Summary of Significant Accounting Policies (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss) at beginning of period	$ 112	$ (393)	$ 34	$ (468)
Total accumulated other comprehensive income (loss) at end of period	(98)	(47)	(98)	(47)
Unrealized Losses On Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss) at beginning of period	(14)	(19)	(6)	(21)
Other comprehensive income (loss) before reclassifications	1	4	(7)	6
Total accumulated other comprehensive income (loss) at end of period	(13)	(15)	(13)	(15)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss) at beginning of period	126	(374)	40	(447)
Other comprehensive income (loss) before reclassifications	(349)	373	(181)	425
Amounts reclassified from accumulated other comprehensive income (loss) to other income (loss)	138	(31)	56	(10)
Total accumulated other comprehensive income (loss) at end of period	$ (85)	$ (32)	$ (85)	$ (32)

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Fair Value [Abstract]
Change in value of contingent consideration	$ (5,916)
Changes in fair value included in earnings	$ (5,916)		$ (4,078)

Fair Value (Financial Assets an

Fair Value (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Total assets	$ 25,805	$ 26,165
Liabilities:
Acquisition-related contingent consideration	31,182	37,098
Total liabilities	31,182	37,098
Money Market Funds [Member]
Assets:
Total assets	2,603	12,774
Commercial Paper [Member]
Assets:
Total assets	8,541	7,472
U.S. Government Securities [Member]
Assets:
Total assets	2,584	2,999
Corporate Bonds [Member]
Assets:
Total assets	8,099	2,920
Asset-backed Securities [Member]
Assets:
Total assets	3,978
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Total assets	2,584	2,999
Liabilities:
Acquisition-related contingent consideration
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Government Securities [Member]
Assets:
Total assets	2,584	2,999
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total assets	23,221	23,166
Liabilities:
Acquisition-related contingent consideration
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]
Assets:
Total assets	2,603	12,774
Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Assets:
Total assets	8,541	7,472
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Assets:
Total assets	8,099	2,920
Significant Other Observable Inputs (Level 2) [Member] | Asset-backed Securities [Member]
Assets:
Total assets	3,978
Significant Other Unobservable Inputs (Level 3) [Member]
Liabilities:
Acquisition-related contingent consideration	31,182	37,098
Total liabilities	$ 31,182	$ 37,098

Fair Value (Level 3 Fair Value

Fair Value (Level 3 Fair Value Measurements Using Significant Other Unobservable Inputs for Acquisition-Related Contingent Consideration) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value [Abstract]
Beginning Balance	$ 37,098	$ 41,176
Amounts acquired
Changes in fair value included in earnings	(5,916)	(4,078)
Ending Balance	$ 31,182	$ 37,098

Intangible Assets (Narative) (D

Intangible Assets (Narative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Intangible Assets [Abstract]
Amortization of intangible assets	$ 342	$ 342	$ 684	$ 684

Intangible Assets (Company's In

Intangible Assets (Company's Intangible Assets) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 55,442	$ 55,442
Accumulated Amortization	$ 5,362	4,678
Fusion Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	10 years
Cost	$ 9,242	9,242
Accumulated Amortization	$ 4,159	3,697
SUBTLE Access Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Cost	$ 2,179	2,179
Accumulated Amortization	1,203	981
IPR&D [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	$ 44,021	$ 44,021

Intangible Assets (Future Amort

Intangible Assets (Future Amortization Expense Related to Intangible Assets with Definite Lives) (Details) $ in Thousands	Jun. 30, 2018USD ($)
Intangible Assets [Abstract]
2,018	$ 683
2,019	1,367
2,020	1,235
2,021	924
2,022	925
2023 and thereafter	925
Total	$ 6,059

Accrued Liabilities (Accrued Li

Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued Liabilities [Abstract]
Accrued commissions	$ 5,416	$ 6,964
Accrued payroll and employee-related expenses	4,370	4,097
Accrued bonus	4,163	4,726
Sales returns and allowances	1,319	1,169
Other accrued liabilities	701	695
Accrued royalties	669	626
Accrued taxes	523	634
Total	$ 17,161	$ 18,911

Indebtedness (Narrative) (Detai

Indebtedness (Narrative) (Details) - USD ($)	Feb. 23, 2018	Apr. 25, 2016	Jun. 30, 2018	Oct. 31, 2015
Line of Credit Facility [Line Items]
Accumulated amortization on the capital leases			$ 2,699,000
Maximum [Member]
Line of Credit Facility [Line Items]
Letter of credit required to landlord			1,250,000
Silicon Valley Bank Agreement [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit			0
Line of credit, availability			$ 18,750,000
Silicon Valley Bank, Second Amended And Restated Loan Agreement [Member]
Line of Credit Facility [Line Items]
Principal payment starting period after inception of loan to maturity	18 months
Silicon Valley Bank, Amended And Restated Loan Agreement Effective 2/23/18 [Member]
Line of Credit Facility [Line Items]
Upon certain conditions met, deferred loan payment period			6 months
Silicon Valley Bank, Amended And Restated Loan Agreement Effective 2/23/18 [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	$ 20,000,000
Maturity date			Feb. 28, 2023
Optional increase in line of credit	$ 20,000,000
Additional fee on total term loan			0.33%
Silicon Valley Bank, Amended And Restated Loan Agreement Effective 2/23/18 [Member] | Revolving Credit Facility [Member] | Prime Rate [Member]
Line of Credit Facility [Line Items]
Basis rate			4.50%
Building And Equipment [Member]
Line of Credit Facility [Line Items]
Capital lease expiration period			Dec. 31, 2030
Cost of assets under lease			$ 14,462,000
Term Loan [Member] | Silicon Valley Bank, Second Amended And Restated Loan Agreement [Member]
Line of Credit Facility [Line Items]
Loan term	5 years
Term Loan [Member] | Silicon Valley Bank, Amended And Restated Loan Agreement Effective 2/23/18 [Member]
Line of Credit Facility [Line Items]
Loan amount	$ 40,000,000
Additional fee on total term loan		3.50%
Accrued fee amount			93,000
Financing costs			$ 744,000
Term Loan [Member] | Silicon Valley Bank, Amended And Restated Loan Agreement Effective 2/23/18 [Member] | Prime Rate [Member]
Line of Credit Facility [Line Items]
Basis rate			3.75%
Interest rate			8.25%
Mason Lease [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Letter of credit outstanding				$ 1,250,000

Indebtedness (Future Maturities

Indebtedness (Future Maturities On Debt And Capital Lease Obligations) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Indebtedness [Abstract]
2,018	$ 736
2,019	5,303
2,020	12,943
2,021	12,947
2,022	12,968
2023 and thereafter	16,260
Total payments	61,157
Imputed interest	(6,676)
Net long-term debt and capital lease obligations, of which $589 is current and $53,892 is noncurrent	54,481
Net capital lease obligations, current	589	$ 561
Net capital lease obligations, noncurrent	$ 53,892

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Commitments and Contingencies [Line Items]
Royalty expense	$ 695	$ 602	$ 1,367	$ 1,136
Minimum [Member]
Commitments and Contingencies [Line Items]
Royalty rates			3.00%
Royalty agreement term			18 years
Maximum [Member]
Commitments and Contingencies [Line Items]
Royalty rates			5.00%
Royalty agreement term			20 years
Office, Manufacturing, Warehouse Facilities, And Equipment [Member]
Commitments and Contingencies [Line Items]
Operating leases expire at various terms			Dec. 31, 2022

Income Tax Provision (Narrative

Income Tax Provision (Narrative) (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Provision [Abstract]
Effective tax rate	(16.64%)	(0.25%)	(0.92%)	(0.23%)
Federal tax at statutory rate			21.00%		35.00%

Equity Compensation Plans (Narr

Equity Compensation Plans (Narrative) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)itemshares	May 31, 2018shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based incentive plans | item	2
Participants purchase limit shares	3,000
Offering period	6 months
Minimum [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Maximum [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of options from the date of grant	10 years
Common stock reserved for issuance	10,249,000
Shares available for future grants	513,000
Shares approved		850,000
2014 Plan [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period beginning	3 years
2008 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	136,000
Company's common stock may be purchased at a discount	15.00%
Participants purchase limit value | $	$ 25
2018 PSAs [Member] | Performance Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting right of shares of common stock	1
Vesting period	3 years
2018 PSAs [Member] | Minimum [Member] | Performance Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance stock award threshold, target and maximum payout opportunity percentage	0.00%
2018 PSAs [Member] | Maximum [Member] | Performance Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance stock award threshold, target and maximum payout opportunity percentage	200.00%
2018 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	500,000
First Anniversary Date Of Grant [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
First Anniversary Date Of Grant [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
First Anniversary Date Of Grant [Member] | 2014 Plan [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	25.00%
Second Anniversary Date Of Grant [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
Second Anniversary Date Of Grant [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
Second Anniversary Date Of Grant [Member] | 2014 Plan [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	25.00%
Third Anniversary Date Of Grant [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
Third Anniversary Date Of Grant [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	0.33%
Third Anniversary Date Of Grant [Member] | 2014 Plan [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	25.00%

Equity Compensation Plans (Shar

Equity Compensation Plans (Share-Based Compensation Expense Related to Employee Share-Based Compensation) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total	$ 3,534	$ 3,697	$ 7,424	$ 7,325
Cost of Revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total	239	138	476	269
Research and Development Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total	361	502	952	1,003
Selling, General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total	$ 2,934	$ 3,057	$ 5,996	$ 6,053

Segment and Geographic Inform42

Segment and Geographic Information (Narrative)(Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Europe [Member]
Long-lived assets	$ 1,006	$ 957

Segment and Geographic Inform43

Segment and Geographic Information (Revenue by Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 51,802	$ 45,231	$ 98,796	$ 86,504
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	40,834	35,534	79,270	68,802
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	6,694	5,688	12,565	10,877
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	4,049	3,785	6,488	6,436
Other International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	225	224	473	389
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 10,968	$ 9,697	$ 19,526	$ 17,702

Segment and Geographic Inform44

Segment and Geographic Information (Revenue by Product Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue from External Customer [Line Items]
Revenue	$ 51,802	$ 45,231	$ 98,796	$ 86,504
United States [Member]
Revenue from External Customer [Line Items]
Revenue	40,834	35,534	79,270	68,802
United States [Member] | Open-heart Ablation [Member]
Revenue from External Customer [Line Items]
Revenue	18,073	16,790	35,652	32,495
United States [Member] | Minimally Invasive Ablation [Member]
Revenue from External Customer [Line Items]
Revenue	9,114	8,725	17,727	17,007
United States [Member] | Appendage Management [Member]
Revenue from External Customer [Line Items]
Revenue	13,101	9,463	24,898	18,165
United States [Member] | Ablation And Appendage Management [Member]
Revenue from External Customer [Line Items]
Revenue	40,288	34,978	78,277	67,667
United States [Member] | Valve Tools [Member]
Revenue from External Customer [Line Items]
Revenue	546	556	993	1,135
International [Member]
Revenue from External Customer [Line Items]
Revenue	10,968	9,697	19,526	17,702
International [Member] | Open-heart Ablation [Member]
Revenue from External Customer [Line Items]
Revenue	5,836	5,674	10,745	10,264
International [Member] | Minimally Invasive Ablation [Member]
Revenue from External Customer [Line Items]
Revenue	2,660	2,135	4,452	4,093
International [Member] | Appendage Management [Member]
Revenue from External Customer [Line Items]
Revenue	2,424	1,777	4,222	3,172
International [Member] | Ablation And Appendage Management [Member]
Revenue from External Customer [Line Items]
Revenue	10,920	9,586	19,419	17,529
International [Member] | Valve Tools [Member]
Revenue from External Customer [Line Items]
Revenue	$ 48	$ 111	$ 107	$ 173