Penumbra (PEN) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 17, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Penumbra Inc
Entity Central Index Key	1,321,732
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		33,938,594

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 65,621	$ 13,236
Marketable investments	153,203	115,517
Accounts receivable, net of doubtful accounts of $1,066 and $684 at September 30, 2017 and December 31, 2016, respectively.	47,964	43,335
Inventories	90,529	73,012
Prepaid expenses and other current assets	14,464	18,727
Total current assets	371,781	263,827
Property, Plant and Equipment, Net	28,259	21,464
Intangible Assets, Net (Excluding Goodwill)	23,821	0
Goodwill	7,449	0
Deferred taxes	22,503	22,476
Other non-current assets	5,281	487
Total assets	459,094	308,254
Current liabilities:
Accounts payable	5,768	4,110
Accrued liabilities	45,312	31,690
Total current liabilities	51,080	35,800
Deferred rent	6,065	5,083
Other non-current liabilities	18,117	824
Total liabilities	75,262	41,707
Commitments and contingencies
Stockholders’ equity:
Common stock	33	31
Additional paid-in capital	389,682	273,865
Accumulated other comprehensive income (loss)	1,204	(4,688)
Accumulated deficit	(7,087)	(2,661)
Total stockholders’ equity	383,832	266,547
Total liabilities and stockholders’ equity	$ 459,094	$ 308,254

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,066	$ 684

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenue	$ 83,911	$ 67,187	$ 237,713	$ 190,212
Cost of revenue	29,134	24,313	84,298	65,963
Gross profit	54,777	42,874	153,415	124,249
Operating expenses:
Research and development	8,132	6,497	23,260	17,762
Sales, general and administrative	45,962	37,740	132,846	106,685
Total operating expenses	54,094	44,237	156,106	124,447
Income (loss) from operations	683	(1,363)	(2,691)	(198)
Interest income, net	658	631	1,926	1,700
Other expense, net	(647)	(360)	(1,368)	(856)
Income (loss) before income taxes	694	(1,092)	(2,133)	646
Provision for (benefit from) income taxes	456	(12,998)	2,293	(16,564)
Net income (loss)	238	11,906	(4,426)	17,210
Foreign currency translation adjustments, net of tax	5,845	(898)	5,771	(1,731)
Unrealized gain (loss) on available-for-sale securities, net of tax	54	(115)	121	254
Comprehensive income	6,137	10,893	1,466	15,733
Net income (loss)	$ 238	$ 11,906	$ (4,426)	$ 17,210
Net (loss) income per share attributable to common stockholders — Basic (in dollars per share)	$ 0.01	$ 0.39	$ (0.14)	$ 0.57
Net (loss) income per share attributable to common stockholders — Diluted (in dollars per share)	$ 0.01	$ 0.35	$ (0.14)	$ 0.52
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Basic (in shares)	33,446,841	30,604,384	32,766,135	30,269,463
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Diluted (in shares)	35,664,272	33,755,383	32,766,135	33,367,618

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (4,426)	$ 17,210
Adjustments to reconcile net (loss) income to net cash provided by (used in) operating activities:
Depreciation and amortization	2,580	1,809
Amortization of premium on marketable investments	501	733
Stock-based compensation	13,092	10,800
Loss on non-marketable equity investments	703	0
Inventory write downs	996	1,190
Other	474	65
Changes in operating assets and liabilities:
Accounts receivable	704	(7,088)
Inventories	(14,716)	(14,018)
Prepaid expenses and other current and non-current assets	3,303	(22,895)
Accounts payable	873	947
Accrued expenses and other non-current liabilities	9,514	8,797
Net cash provided by (used in) operating activities	13,598	(2,450)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of a business, net of cash acquired	(9,253)	0
Purchase of non-marketable investments	(5,130)	0
Purchase of marketable investments	(139,317)	(45,027)
Proceeds from sales of marketable investments	28,167	2,504
Proceeds from maturities of marketable investments	73,579	46,081
Acquisition of intangible assets from a licensing agreement	(2,500)	0
Purchases of property and equipment	(6,805)	(7,078)
Net cash used in investing activities	(61,259)	(3,520)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance cost	106,265	0
Proceeds from exercises of stock options	4,244	2,893
Proceeds from issuance of stock under employee stock purchase plan	2,914	3,783
Payment of employee taxes related to vested restricted stock	(10,569)	(2,024)
Payment of obligations on debt and credit facilities	(940)	0
Net cash provided by financing activities	101,914	4,652
Effect of foreign exchange rate changes on cash and cash equivalents	(1,868)	(2,373)
Net Increase (Decrease) in Cash and Cash Equivalents	52,385	(3,691)
CASH AND CASH EQUIVALENTS—Beginning of period	13,236	19,547
CASH AND CASH EQUIVALENTS—End of period	65,621	15,856
NONCASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment funded through accounts payable and accrued liabilities	2,933	2,197
Acquisition-related contingent consideration and working capital adjustment liabilities	4,897	0
Licensing agreement related contingent consideration	$ 12,717	$ 0

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business Penumbra, Inc. (the “Company”) is a global healthcare company focused on interventional therapies. The Company designs, develops, manufactures and markets innovative devices and has a broad portfolio of products that addresses challenging medical conditions and significant clinical needs across two major markets, neuro and peripheral vascular. The conditions that the Company’s products address include, among others, ischemic stroke, hemorrhagic stroke and various peripheral vascular conditions that can be treated through thrombectomy and embolization procedures.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying condensed consolidated balance sheet as of September 30, 2017 , the condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 , and the condensed consolidated statements of cash flows for the nine months ended September 30, 2017 and 2016 are unaudited. The unaudited condensed consolidated financial statements included herein have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and the applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. The condensed consolidated balance sheet as of December 31, 2016 was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company’s financial position as of September 30, 2017 , the results of its operations for the three and nine months ended September 30, 2017 and 2016 , and the cash flows for the nine months ended September 30, 2017 and 2016 . The results for the three and nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 or for any other future annual or interim period. Certain changes in presentation were made in the condensed consolidated financial statements for the three and nine months ended September 30, 2016 , to conform to the presentation for the three and nine months ended September 30, 2017 . The Company elected to early adopt Accounting Standards Update ( “ ASU ” ) 2016-09 in the fourth quarter of 2016 which requires the Company to reflect any adjustments as of January 1, 2016, the beginning of the annual period that includes the interim period of adoption. The impact of adoption was the creation of deferred tax assets (“DTAs”) in the balance sheet and recognition of excess tax benefits in our provision for (benefit from) income taxes rather than paid-in capital for all periods in fiscal year 2016. The Company elected to apply the presentation requirements for cash flows related to excess tax benefits retrospectively to all periods presented. Adoption of the new standard resulted in adjustments to our 2016 unaudited selected financial data previously reported in our Quarterly Report on Form 10-Q as follows: September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Balance Sheet Data: Prepaid expenses and other current assets $ 18,665 $ 19,209 Total current assets 267,223 267,767 Deferred taxes 13,394 22,059 Total assets 297,279 306,488 Other non-current liabilities 6,081 5,540 Total liabilities 43,425 42,884 Additional paid-in-capital 275,031 267,429 Accumulated deficit (17,616 ) (264 ) Total stockholders ’ equity 253,854 263,604 Total liabilities and stockholders ’ equity 297,279 306,488 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2016 (In thousands, except per share amounts) As Previously Reported As Adjusted As Previously Reported As Adjusted Condensed Consolidated Statements of Operations Data: Provision for (benefit from) income taxes $ 14 $ (12,998 ) $ 787 $ (16,564 ) Net (loss) income $ (1,106 ) $ 11,906 $ (141 ) $ 17,210 Net (loss) income per share: Basic $ (0.04 ) $ 0.39 $ 0.00 $ 0.57 Diluted $ (0.04 ) $ 0.35 $ 0.00 $ 0.52 Weighted average shares used to compute net (loss) income per share attributable to common stockholders: Basic 30,604,384 30,604,384 30,269,463 30,269,463 Diluted 30,604,384 33,755,383 30,269,463 33,367,618 Nine Months Ended September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Statement of Cash Flow Data: Net cash used in operating activities $ (10,051 ) $ (2,450 ) Net cash provided by financing activities $ 12,253 $ 4,652 The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2016 , included in the Company’s Annual Report on Form 10-K. During the nine months ended September 30, 2017 , the Company added accounting policies for goodwill, contingent consideration, intangible assets and non-marketable equity investments as described below. There have been no other changes to the Company’s significant accounting policies during the nine months ended September 30, 2017 , as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 . The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and equity accounts; disclosure of contingent assets and liabilities at the date of the financial statements; and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, including those related to marketable investments, provisions for doubtful accounts, sales return reserve, warranty reserve, valuation of inventories, useful lives of property and equipment, income taxes, and contingencies, among others. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other data. Actual results could differ from those estimates. Goodwill Goodwill represents the excess of the purchase price of an acquired business or assets over the fair value of the identifiable assets acquired and liabilities assumed. Goodwill is not amortized, but is tested for impairment at least annually, or more frequently if events or circumstances indicate the carrying value may no longer be recoverable and that an impairment loss may have occurred. The Company continues to operate as one segment, which is considered to be the sole reporting unit, and therefore goodwill is tested for impairment at the consolidated level. As of September 30, 2017 , the Company’s goodwill is related to the acquisition of Crossmed S.p.a (“Crossmed”) during the third quarter of 2017 . Refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ” for more information. Contingent Consideration Certain agreements the Company enters into, including business combinations and licensing agreements, involve the potential payment of future consideration that is contingent upon certain performance and revenue milestones being achieved. Contingent consideration related to business combinations is recorded at the acquisition date at fair value and is remeasured each reporting period with the change in fair value recognized within sales, general and administrative expense in the consolidated statements of operations and comprehensive income . As of September 30, 2017 , the Company’s contingent consideration related to the acquisition of Crossmed and intangible assets through a licensing agreement. For more information with respect to the fair value of contingent consideration, refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ,” respectively. Intangible Assets Intangible assets consist of intangibles acquired through a licensing arrangement and the acquisition of Crossmed during the third quarter of 2017. Indefinite-lived intangible assets relate to payments and future milestone payments, which are probable and estimable, for an exclusive right to licensed technology. The acquired licensed technology is accounted for as an indefinite-lived intangible asset until it reaches technological feasibility, which is determined on the basis of obtaining regulatory approval to market and commercialize the underlying products. Upon the commercialization of the underlying product, the capitalized amount will be amortized over its estimated useful life. Indefinite-lived intangible assets will be tested for impairment at least annually, or more frequently if events or circumstances indicate their carrying value may no longer be recoverable and that an impairment loss may have occurred. Finite-lived intangible assets are amortized using the straight-line method over the estimated economic useful lives of the assets, which is the period during which expected cash flows support the fair value of such intangible assets. The Company will review finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When such an event occurs, management will determine whether there has been impairment by comparing the anticipated undiscounted future net cash flows to the related asset group’s carrying value. If an asset is considered impaired, the asset will be written down to the determined fair value based on discounted cash flows. Refer to Note “ 6. Goodwill and Intangible Assets ” for more information on the Company’s intangible assets. Non-Marketable Equity Investments Entities in which the Company has at least a 20% , but not more than a 50% , interest are accounted for under the equity method unless it is determined that the Company has a controlling financial interest in the entity, in which case the entity would be consolidated. Non-marketable equity investments are classified as investments and included in other non-current assets on the condensed consolidated balance sheet . The Company’s proportionate share of the operating results of its non-marketable equity method investments are recorded as profit or loss and included as a component of other expense, net, in the condensed consolidated statements of operations and comprehensive income . See Note “ 3. Investments and Fair Value of Financial Instruments ” for further details. Segments The Company determined its operating segment on the same basis that it uses to evaluate its performance internally. The Company has one business activity: the design, development, manufacturing and marketing of innovative devices, and operates as one operating segment. The Company’s chief operating decision-maker, its Chief Executive Officer, reviews its operating results for the purpose of allocating resources and evaluating financial performance. The Company assigns revenue to a geographic area based on the destination to which it ships its products. Recent Accounting Guidance Recently Adopted Accounting Standards In July 2015, the Financial Accounting Standards Board ( “ FASB ”) issued ASU No. 2015-11, Simplifying the Measurement of Inventory , which requires an entity to measure most inventory at the lower of cost and net realizable value, thereby simplifying the current guidance under which an entity must measure inventory at the lower of cost or market. In January 2017, the Company adopted the standard on a prospective basis and the adoption did not have a material impact on its financial position. Recently Issued Accounting Standards In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which outlines a comprehensive new revenue recognition model designed to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers — Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which further clarifies the implementation guidance on principal versus agent considerations contained in ASU No. 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers — Identifying Performance Obligations and Licensing , which further clarifies the implementation guidance relating to identifying performance obligations and the licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers — Narrow-Scope improvements and Practical Expedients , which further clarifies the implementation on narrow scope improvements and practical expedients. In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606 — Revenue from Contracts with Customer s , which makes minor corrections or minor improvements to the Codification related to ASU No. 2014-09 that are not expected to have a significant effect on the Company ’ s current accounting practice. In September 2017, the FASB issued ASU No. 2017-13, Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842): Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments , (“ASU No. 2017-13”) which provides additional clarification and implementation guidance on the previously issued ASU No. 2014-09. These standards will be effective for the Company in the first quarter of 2018 pursuant to ASU No. 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date , issued by the FASB in August 20 15. The Company intends to adopt the new standard on a modified retrospective basis on January 1, 2018. Under this method, the C ompany will record a cumulative-effect adjustment to the opening balance of retained earnings in the initial year of adoption. The timing of revenue recognition based on the guidance related to transfer of control may result in acceleration of revenue recognition for some contracts. The Company does not expect the impact of the new standard to be material, but it expands financial statement disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. As we continue our assessment through the remainder of 2017, our preliminary assessment is subject to change. In February 2016, the FASB issued ASU No. 2016-02, Leases, which amends the existing accounting standards for leases. In September 2017, the FASB issued ASU No. 2017-13 which provides additional clarification and implementation guidance on the previously issued ASU No. 2016-02. Under the new guidance, a lessee will be required to recognize a lease liability and right-of-use asset for all leases with terms in excess of twelve months. The new guidance also modifies the classification criteria and accounting for sales-type and direct financing leases, and requires additional disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. Consistent with current guidance, a lessee’s recognition, measurement, and presentation of expenses and cash flows arising from a lease will continue to depend primarily on its classification. The accounting standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and must be applied using a modified retrospective approach. Early adoption is permitted. While the Company is continuing to assess all potential impacts of the standard, it expects that most of its lease commitments will be subject to the updated standard and recognized as lease liabilities and right-of-use assets upon adoption. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses . The standard changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The Company will recognize an allowance for credit losses on available-for-sale securities rather than deductions in amortized cost. The standard is effective for fiscal years and interim periods beginning after December 15, 2019. Early adoption is permitted for all periods beginning after December 15, 2018. The Company is currently evaluating the impact of adopting this standard. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows: Restricted Cash , a consensus of the FASB Emerging Issues Task Force . The standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling the total beginning and end of period amounts shown on the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. The Company does not expect the adoption of ASU 2016-18 to have a material impact on its consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation - Scope of Modification Accounting. The standard provides clarification on when modification accounting should be used for changes to the terms or conditions of a share-based payment award. This standard does not change the accounting for modifications but clarifies that modification accounting guidance should only be applied if there is a change to the value, vesting conditions, or award classification and would not be required if the changes are considered non-substantive. The standard is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. Early adoption is permitted. The guidance will be applied prospectively upon adoption. The Company does not expect the adoption of ASU 2017-09 to have a material impact on its consolidated financial statements, however the impact to share-based compensation expense will depend on the terms specified in any new changes to share-based payment awards subsequent to the adoption.

Investments and Fair Value of F

Investments and Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. Investments and Fair Value of Financial Instruments Marketable Investments The Company’s marketable investments have been classified and accounted for as available-for-sale. The Company’s marketable investments as of September 30, 2017 and December 31, 2016 were as follows (in thousands): September 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 23,471 $ 2 $ (1 ) $ 23,472 U.S. Treasury 9,004 — (4 ) 9,000 U.S. agency and government sponsored securities 3,600 — (8 ) 3,592 U.S. states and municipalities 10,207 1 (4 ) 10,204 Corporate bonds 106,964 48 (77 ) 106,935 Total $ 153,246 $ 51 $ (94 ) $ 153,203 December 31, 2016 Amortized Cost Gross Gross Fair Value Commercial paper $ 4,237 $ 1 $ — $ 4,238 U.S. Treasury 4,996 — — 4,996 U.S. agency and government sponsored securities 8,803 3 (12 ) 8,794 U.S. states and municipalities 27,429 1 (75 ) 27,355 Corporate bonds 69,009 36 (120 ) 68,925 Non-U.S. government debt securities 1,209 — — 1,209 Total $ 115,683 $ 41 $ (207 ) $ 115,517 The following tables present the gross unrealized losses and the fair value for those marketable investments that were in an unrealized loss position for less than and more than twelve months as of September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 Less than 12 months 12 months or more Total Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Commercial paper $ 10,959 $ (1 ) $ — $ — $ 10,959 $ (1 ) U.S. Treasury 9,000 (4 ) — — 9,000 (4 ) U.S. agency and government sponsored securities 1,600 — 1,992 (8 ) 3,592 (8 ) U.S. states and municipalities 7,184 (4 ) — — 7,184 (4 ) Corporate bonds 49,655 (48 ) 4,168 (29 ) 53,823 (77 ) Total $ 78,398 $ (57 ) $ 6,160 $ (37 ) $ 84,558 $ (94 ) December 31, 2016 Less than 12 months Fair Value Gross Unrealized Losses U.S. agency and government sponsored securities $ 3,291 $ (12 ) U.S. states and municipalities 22,286 (75 ) Corporate bonds 29,748 (120 ) Total $ 55,325 $ (207 ) As of December 31, 2016 , there were no securities that had been in a loss position for more than twelve months. The contractual maturities of the Company’s marketable investments as of September 30, 2017 and December 31, 2016 were as follows (in thousands): September 30, December 31, 2016 Fair Value Fair Value Due in less than one year $ 122,829 $ 71,051 Due in one to five years 30,374 44,466 Total $ 153,203 $ 115,517 Non-Marketable Equity Investments In May 2017, the Company and an unrelated third-party formed a privately-held company, MVI Health Inc. ( “ MVI ” ), with each party holding 50% of the issued and outstanding equity of MVI. The Company accounted for its investment under the equity method and is not required to consolidate MVI under the voting model. As of September 30, 2017 , the Company determined that MVI was not a variable interest entity ( “VIE” ). The Company will reassess in subsequent periods whether MVI becomes a VIE due to changes in facts and circumstances, including changes to the sufficiency of the equity investment at risk, management and governance structure or capital structure. As of September 30, 2017 , the carrying value of the non-marketable equity investment was approximately $4.4 million , representing the Company ’s contributions to MVI offset by the Company ’s share of equity method investee losses. The non-marketable equity method investment is included in other non-current assets on the condensed consolidated balance sheet. During the three and nine months ended September 30, 2017 , MVI recorded a net loss of $1.1 million and $1.4 million , respectively, from operating expenses in the same amounts. The Company reflected its 50% share of investee losses for the three and nine months ended September 30, 2017, of $0.5 million and $0.7 million , respectively, as a component of other expense, net, in the condensed consolidated statements of operations and comprehensive income . The Company held no non-marketable equity investments in 2016 . Fair Value of Financial Instruments Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value: 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 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 categorization of a financial instrument within the valuation hierarchy is based on the lowest level of input that is significant to the fair value measurement. The Company classifies its cash equivalents and marketable investments within Level 1 and Level 2, as it uses quoted market prices or alternative pricing sources and models utilizing market observable inputs. The Company determined the fair value of its Level 1 financial instruments, which are traded in active markets, using quoted market prices for identical instruments. Financial instruments classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, the Company relies on non-binding quotes from its investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers. To validate the fair value determination provided by its investment managers, the Company reviews the pricing movement in the context of overall market trends and trading information from its investment managers. In addition, the Company assesses the inputs and methods used in determining the fair value in order to determine the classification of securities in the fair value hierarchy. The following table sets forth the Company’s financial assets measured at fair value by level within the fair value hierarchy (in thousands): As of September 30, 2017 Level 1 Level 2 Total Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 9,084 $ 9,084 Money market funds 9,042 — 9,042 U.S. Treasury — — — U.S. states and municipalities — 6,500 6,500 Marketable investments: Commercial paper — 23,472 23,472 U.S. Treasury 9,000 — 9,000 U.S. agency and government sponsored securities — 3,592 3,592 U.S. states and municipalities — 10,204 10,204 Corporate bonds — 106,935 106,935 Total $ 18,042 $ 159,787 $ 177,829 As of December 31, 2016 Level 1 Level 2 Total Fair Value Financial Assets Cash equivalents: Money market funds $ 873 $ — $ 873 Marketable investments: Commercial paper — 4,238 4,238 U.S. Treasury 4,996 — 4,996 U.S. agency and government sponsored securities — 8,794 8,794 U.S. states and municipalities — 27,355 27,355 Corporate bonds — 68,925 68,925 Non-U.S. government debt securities — 1,209 1,209 Total $ 5,869 $ 110,521 $ 116,390 During the nine months ended September 30, 2017 and 2016 , the Company did not record impairment charges related to its marketable investments and the Company did not hold any Level 3 marketable investments as of September 30, 2017 or December 31, 2016 . In addition to the amounts presented above, the Company recorded contingent consideration liabilities at fair value during 2017. During the three months ended September 30, 2017, the Company acquired Crossmed and recorded contingent consideration in the amount of $4.3 million . Also during the three months ended September 30, 2017, the Company entered into an exclusive technology license agreement and recorded contingent consideration in the amount of $12.7 million . These contingent consideration liabilities are classified as Level 3 measurements for which fair value is derived from significant unobservable inputs, such as projected revenue and estimates in the timing and likelihood of achieving revenue-based milestones. During the three months ended September 30, 2017 , there were no changes in fair value for these contingent consideration liabilities . For more information with respect to the fair value of contingent consideration, refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ,” respectively. During the nine months ended September 30, 2017 and 2016 , the Company did not have any transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy. Additionally, the Company did not have any financial assets and liabilities measured at fair value on a non-recurring basis as of September 30, 2017 or December 31, 2016 .

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Prepaid Expenses and Other Current Assets The following table shows the components of prepaid expenses and other current assets as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Prepaid tax $ 1,023 $ 4,656 Prepaid expenses 5,213 4,573 Other current assets 8,228 9,498 Prepaid expenses and other current assets $ 14,464 $ 18,727 Inventories The following table shows the components of inventories as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Raw materials $ 11,288 $ 11,367 Work in process 6,923 3,663 Finished goods 72,318 57,982 Inventories $ 90,529 $ 73,012 Accrued Liabilities The following table shows the components of accrued liabilities as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Payroll and employee-related cost $ 22,244 $ 16,956 Sales return reserve 3,024 2,753 Preclinical and clinical trial cost 1,501 2,054 Royalty 946 802 Product warranty 1,066 1,254 Leasehold improvement expenditures 2,904 260 Acquisition-related liabilities 1 3,514 — Other accrued liabilities 10,113 7,611 Total accrued liabilities $ 45,312 $ 31,690 1 Acquisition-related liabilities consistent of contingent consideration related to the cash milestone payments and working capital adjustment liabilities for the acquisition of Crossmed. Refer to Note “ 5. Business Combination ” for more information. The following table shows the changes in the Company’s estimated product warranty accrual, included in accrued liabilities, as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Balance at the beginning of the period $ 1,254 $ 713 Accruals of warranties issued 289 1,176 Settlements of warranty claims (477 ) (635 ) Balance at the end of the period $ 1,066 $ 1,254 Other Non-Current Liabilities The following table shows the components of other non-current liabilities as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Deferred tax liabilities $ 3,299 $ 824 Licensing-related cost 1 12,717 — Other non-current liabilities 2,101 — Total other non-current liabilities $ 18,117 $ 824 1 Amount relates to the liability recorded for probable future milestone payments to be made under the licensing agreement described in Note “ 6. Goodwill and Intangible Assets ,” refer therein for more information.

Business Combination

Business Combination	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Business Combination	5. Business Combination On July 3, 2017 (the “Closing Date”), the Company completed the acquisition of Crossmed, a joint stock company organized under the laws of Italy. Crossmed is engaged in the business of distributing medical supplies and equipment in Italy, San Marino, the Vatican, and Switzerland. Crossmed was the Company’s exclusive distributor in Italy, San Marino and the Vatican and the acquisition provides the Company with a direct relationship with its customers in these regions. As of the Closing Date, Crossmed became a wholly-owned subsidiary of the Company and is being integrated into the Company’s core business. The acquisition of Crossmed does not result in any changes to the Company’s operating or reportable segment structure and the Company continues to operate as one operating segment. The following table summarizes the Closing Date fair value of the consideration transferred (in thousands): Cash, net of working capital and financial debt adjustments $ 9,918 Fair value of contingent consideration for milestone payments 4,343 Contract purchase price $ 14,261 Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra 3,273 Total value of consideration transferred $ 17,534 Upon the Closing Date, the Company paid the sellers of Crossmed an initial payment of €8.2 million , or approximately $9.4 million , subject to post-closing adjustments for working capital and financial debt. The Company will pay additional consideration in the form of milestone payments based on Crossmed’s net revenue, and may pay additional consideration based on incremental net revenue, for each of the years ending December 31, 2017, 2018 and 2019. There is no limit on the milestone payments that can be paid out. The Company recorded a current and non-current liability in the amount of $3.0 million and $1.3 million as of September 30, 2017 , respectively, for the fair value of contingent consideration related to the cash milestone payments. The contingent consideration is classified as a Level 3 measurement for which fair value is derived from inputs that are unobservable and significant to the overall fair value measurement. The fair value of such milestone payments is estimated using a Monte Carlo simulation model that utilizes key assumptions including forecasted revenues during the earn-out period and revenue and asset volatilities. The fair value of the contingent consideration liability will be evaluated each reporting period and changes in its fair value will be included in the Company’s results of operations. There were no changes to the Closing Date fair value of the contingent consideration during the three months ended September 30, 2017 . The preliminary allocation of the purchase price was based upon a preliminary valuation and the Company’s estimates and assumptions are subject to change within the measurement period (generally one year from the Closing Date). The following table presents the preliminary allocation of the purchase price for Crossmed (in thousands): Acquisition-Date Fair Value Estimated Useful Life of Finite-Lived Intangible Assets Tangible assets acquired and (liabilities) assumed: Accounts receivable $ 4,406 Inventories 1,343 Other current and non-current assets 1,316 Property and equipment, net 829 Accounts payable (740 ) Accrued liabilities and obligations for short-term debt and credit facilities (2,164 ) Deferred tax liabilities (2,472 ) Other non-current liabilities (797 ) Intangible assets acquired: Customer relationships $ 6,790 15 years Other 1,750 5 years Goodwill 7,273 Total purchase price $ 17,534 Acquired intangible assets are classified as Level 3 measurements for which fair value is derived from valuations based on inputs that are unobservable and significant to the overall fair value measurement. The Company used the income approach, specifically the discounted cash flow method and the incremental cash flow approach, to derive the fair value of the customer relationships and other intangible assets. Customer relationships are direct relationships with physicians and hospitals performing procedures with the distributed products. Other intangibles consists of non-Penumbra supplier relationships and sub-distributor relationships with third parties used to sell products, both as of the Closing Date. The intangible assets are amortized on a straight-line basis over their assigned estimated useful lives. The acquired intangible assets will not be amortized for tax purposes. As a result, a $2.5 million deferred tax liability was recorded as of September 30, 2017 . The goodwill arising from the Crossmed acquisition is primarily attributed to expected synergies from future growth and assembled workforce. Goodwill will not be deductible for tax purposes. The amount of Crossmed’s net revenue and net loss included in the Company’s condensed consolidated statements of operations and comprehensive income was $2.7 million and $0.3 million , respectively, for each of the three and nine months ended September 30, 2017 The following table presents certain unaudited pro forma information, for illustrative purposes only, for the three and nine months ended September 30, 2017 , as if Crossmed had been acquired on January 1, 2016. The unaudited estimated pro forma information combines the historical results of Crossmed with the Company’s consolidated historical results and includes certain adjustments reflecting the estimated impact of fair value adjustments for the respective periods. The pro forma information is not indicative of what would have occurred had the acquisition taken place on January 1, 2016 and is not indicative of the Company’s future consolidated results. Additionally, the pro forma financial information does not include the impact of possible business model changes and does not reflect pro forma adjustments to conform accounting policies between Crossmed and the Company. The unaudited pro forma information is presented below (unaudited, in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Pro forma net revenue $ 83,911 $ 68,012 $ 240,506 $ 193,521 Pro forma net income (loss) 238 11,950 (4,695 ) 17,020

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	6. Goodwill and Intangible Assets Goodwill The following table presents the changes in goodwill during the nine months ended September 30, 2017 (in thousands): Total Company Balance as of December 31, 2016 $ — Acquisition of Crossmed (1) 7,273 Foreign currency translation 176 Balance as of September 30, 2017 $ 7,449 1 Goodwill includes a $2.5 million adjustment for the relative impact of recording the deferred tax liability associated with the acquired intangible assets of Crossmed. Refer to Note “ 5. Business Combination ” for more information. Goodwill is not amortized, but will be tested for impairment at least annually in the fourth quarter, or more frequently if events or circumstances indicate the carrying value may no longer be recoverable and that an impairment loss may have occurred. Acquired Intangible Assets The following table presents details of the Company’s acquired definite-lived and indefinite-lived intangible assets (in thousands, except weighted-average amortization period): As of September 30, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15 years $ 7,044 $ (168 ) $ 6,876 Other 5 years 1,815 (87 ) 1,728 Total intangible assets subject to amortization $ 8,859 $ (255 ) $ 8,604 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,076 $ (255 ) $ 23,821 The total intangible assets subject amortization relate to the acquisition of Crossmed during the third quarter of 2017. During both the three and nine months ended September 30, 2017 , the Company recorded amortization expense of $0.3 million in sales, general and administrative expense related to the Company’s finite-lived intangible assets . Refer to Note “ 5. Business Combination ” for more information. Licensed technology During the third quarter of 2017, the Company entered into an exclusive technology license agreement (the “License Agreement”) that required the Company to pay an upfront payment to the licensor of $2.5 million and future revenue milestone-based payments on sales of products covered by the licensed intellectual property. The Company recorded an intangible asset of $15.2 million and a corresponding liability for the future milestone payments. The licensed technology is accounted for as an indefinite-lived intangible asset. Once regulatory approval is received to market and commercialize products utilizing the underlying technology, the Company will begin amortizing the intangible asset. As of September 30, 2017, the Company has recorded a contingent consideration liability of $12.7 million included in other non-current liabilities on the consolidated balance sheet related to probable future milestone payments under the Licensing Agreement. The contingent consideration is classified as Level 3 measurement for which fair value is derived from valuation based on inputs that are unobservable and significant to the overall fair value measurement. The fair value of such milestone payments is estimated using key assumptions which include projected revenue and estimates in the timing of when the revenue-based milestones are earned. The fair value of the contingent consideration liability will be evaluated each reporting period.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Lease Commitments The Company leases its offices under non-cancelable operating and capital leases that expire at various dates from 2029 to 2031. Rent expense for non-cancelable operating leases with scheduled rent increases is recognized on a straight-line basis over the lease term. Rent expense for the three months ended September 30, 2017 and 2016 was $1.4 million and $1.4 million , respectively and for the nine months ended September 30, 2017 and 2016 was $4.3 million and $3.8 million , respectively. In addition, the Company’s lease commitments also require it to make additional payments during the lease term for taxes, insurance and other operating expenses. The Company leases its other equipment under non-cancelable operating and capital leases that expire at various dates through 2021 . Royalty Obligations In March 2005, the Company entered into a license agreement that requires the Company to make minimum royalty payments to the licensor on a quarterly basis. As of both September 30, 2017 and December 31, 2016 , the license agreement required minimum annual royalty payments of $0.1 million in equal quarterly installments. On each January 1, the quarterly calendar year minimum royalty will be adjusted to equal the prior year’s minimum royalty adjusted by a percentage equal to the percentage change in the “consumer price index for all urban consumers” for the prior calendar year as reported by the U.S. Department of Labor. Unless terminated earlier, the term of the license agreement will continue until the expiration of the last to expire patent that covers that licensed product or 2022, whichever is longer. In April 2012, the Company entered into an agreement that requires the Company to pay, on a quarterly basis, a 5% royalty on sales of products covered under applicable patents. Unless the agreement is terminated earlier, the royalty term for each applicable product will continue until the expirations of the applicable patents covering such product or 2029, whichever is longer. In November 2013, the Company entered into an agreement that requires the Company to pay, on a quarterly basis, a 3% royalty on the first $5 million in sales and a 1% royalty on sales thereafter of products covered under applicable patents. Unless the agreement is terminated earlier, the royalty for each covered product shall continue until 2030. In April 2015, the Company entered into a royalty agreement that requires the Company to pay, on a quarterly basis, a 2% royalty on sales of certain products covered by the agreement. Unless the royalty agreement is terminated earlier, the royalty term for each covered product shall continue until 2035. Royalty expense included in cost of revenue for the three months ended September 30, 2017 and 2016 was $1.0 million and $0.7 million , respectively and for the nine months ended September 30, 2017 and 2016 was $3.0 million and $2.1 million , respectively. Contingencies From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of business. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. Refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ” for more information on contingent liabilities recorded on the condensed consolidated balance sheet. Indemnification The Company enters into standard indemnification arrangements in the ordinary course of business. In many such arrangements, the Company agrees to indemnify, hold harmless, and reimburse the indemnified parties for losses suffered or incurred by the indemnified parties in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third-party with respect to the Company’s technology. The Company also agrees to indemnify many purchasers for product defect and similar claims. The term of these indemnification agreements is generally perpetual. The maximum potential amount of future payments the Company could be required to make under these agreements is not determinable because it involves claims that may be made against the Company in the future, but have not yet been made. The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers, other than liabilities arising from willful misconduct of the individual. The Company has not incurred costs to defend lawsuits or settle claims related to these indemnification agreements. No liability associated with any of these indemnification requirements has been recorded to date. Litigation The Company was contacted in 2015 by the attorney for a potential product liability claimant who allegedly suffered injuries as a result of an aneurysm procedure in which the Penumbra Coil 400 was used. On February 19, 2016, a complaint for damages was filed on behalf of this claimant against the Company and the hospital involved in the procedure ( Montgomery v. Penumbra, Inc., et al., Case No. 16-2-04050-1 SEA, Superior Court of the State of Washington, King County) . The suit alleges liability primarily under the Washington Product Liability Act (“WPLA”) and sought both compensatory and punitive damages without a specific damages claim. Based on the Company’s preliminary motion, the punitive damages claim was dismissed in May 2016, along with several of the other causes of actions subsumed by the WPLA. In recent submissions, plaintiffs claimed economic and non-economic damag es in an amount substantially in excess of the Company’s insurance coverage. The parties reached a preliminary agreement to settle this matter on confidential terms at a mediation held November 1, 2017. The settlement is subject to finalization and does not have a material financial impact on the Company. If for any reason the settlement is not finalized, the case would continue in the discovery phase, with a trial currently set for April 2018. The Company would continue to vigorously defend the litigation, as the Company believes there are substantial questions regarding causation, liability and damages. If the case proceeds to trial, the results of any jury trial and the damages that a jury might award are inherently uncertain. From time to time, the Company is subject to other claims and assessments in the ordinary course of business. The Company is not currently a party to any such litigation matter that, individually or in the aggregate, is expected to have a material adverse effect on the Company’s business, financial condition, results of operations or cash flows.

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholder's Equity	8. Stockholders’ Equity Common Stock In March 2017, the Company issued and sold an aggregate of 1,495,000 shares of common stock at a public offering price of $76.00 per share, less the underwriters ’ discounts and commissions, pursuant to an underwritten public offering . The Company received approximately $106.3 million in net cash proceeds after deducting underwriting discounts and commissions of $6.8 million and other offering expenses of $0.5 million . Equity Incentive Plans Stock Options Activity of stock options under the Penumbra, Inc. 2005 Stock Plan, the Penumbra, Inc. 2011 Equity Incentive Plan and the Amended and Restated Penumbra, Inc. 2014 Equity Incentive Plan (collectively the “Plans”) during the nine months ended September 30, 2017 is set forth below: Number of Shares Weighted-Average Exercise Price Balance at December 31, 2016 2,876,955 $ 14.63 Options exercised (678,825 ) 6.21 Options canceled (2,866 ) 16.98 Balance at September 30, 2017 2,195,264 17.24 Restricted Stock and Restricted Stock Units Activity of unvested restricted stock and restricted stock units under the Plans during the nine months ended September 30, 2017 is set forth below: Number of Shares Weighted -Average Grant Date Fair Value Unvested at December 31, 2016 1,002,944 $ 29.44 Granted 99,638 80.04 Vested (325,023 ) 24.79 Canceled/Forfeited (20,687 ) 45.22 Unvested and expected to vest at September 30, 2017 756,872 37.67 Stock-based Compensation The following table sets forth the stock-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of revenue $ 316 $ 83 $ 817 $ 742 Research and development 352 251 913 790 Sales, general and administrative 3,819 3,930 11,362 9,268 Total $ 4,487 $ 4,264 $ 13,092 $ 10,800 As of September 30, 2017 , total unrecognized compensation cost was $30.2 million related to unvested share-based compensation arrangements which is expected to be recognized over a weighted average period of 2.4 years. The total stock-based compensation cost capitalized in inventory was $0.2 million and $0.4 million as of September 30, 2017 and December 31, 2016 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	9. Accumulated Other Comprehensive Income (Loss) Other comprehensive income (loss) consists of two components: unrealized gains or losses on the Company’s available-for-sale marketable investments and gains or losses from foreign currency translation adjustments. Until realized and reported as a component of net income (loss), these comprehensive income (loss) items accumulate and are included within accumulated other comprehensive income (loss). Unrealized gains and losses on the Company’s marketable investments are reclassified from accumulated other comprehensive income (loss) into earnings when realized upon sale, and are determined based on specific identification of securities sold. Gains and losses from the translation of assets and liabilities denominated in non-U.S. dollar functional currencies are included in accumulated other comprehensive income (loss). The following table summarizes the changes in the accumulated balances during the three and nine months ended September 30, 2017 and 2016 , and includes information regarding the manner in which the reclassifications out of accumulated other comprehensive income (loss) into earnings affect the Company’s condensed consolidated statements of operations and comprehensive income (in thousands): Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (38 ) $ (4,657 ) $ (4,695 ) $ 206 $ (2,785 ) $ (2,579 ) Other comprehensive income before reclassifications: Unrealized gains (losses) — marketable investments 54 — 54 (178 ) — (178 ) Foreign currency translation gains (losses) — 5,845 5,845 — (901 ) (901 ) Income tax effect — benefit — — — 63 3 66 Net of tax 54 5,845 5,899 (115 ) (898 ) (1,013 ) Amounts reclassified from accumulated other comprehensive income to earnings: Realized losses — marketable investments — — — 1 — 1 Income tax effect — expense — — — (1 ) — (1 ) Net of tax — — — — — — Net current-year other comprehensive income (loss) 54 5,845 5,899 (115 ) (898 ) (1,013 ) Balance at end of the period $ 16 $ 1,188 $ 1,204 $ 91 $ (3,683 ) $ (3,592 ) Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (105 ) $ (4,583 ) $ (4,688 ) $ (163 ) $ (1,952 ) $ (2,115 ) Other comprehensive income before reclassifications: Unrealized gains —marketable investments 157 — 157 401 — 401 Foreign currency translation gains (losses) — 5,771 5,771 — (1,732 ) (1,732 ) Income tax effect — (expense) benefit — — — (145 ) 1 (144 ) Net of tax 157 5,771 5,928 256 (1,731 ) (1,475 ) Amounts reclassified from accumulated other comprehensive income to earnings: Realized gains — marketable investments (36 ) — (36 ) (3 ) — (3 ) Income tax effect — benefit — — — 1 — 1 Net of tax (36 ) — (36 ) (2 ) — (2 ) Net current-year other comprehensive income (loss) 121 5,771 5,892 254 (1,731 ) (1,477 ) Balance at end of the period $ 16 $ 1,188 $ 1,204 $ 91 $ (3,683 ) $ (3,592 )

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The Company’s income tax expense, DTAs and liabilities, and reserves for unrecognized tax benefits reflect management’s best assessment of estimated current and future taxes to be paid. The Company is subject to income taxes in both the United States and foreign jurisdictions. Significant judgment and estimates are required in determining the consolidated income tax expense. During interim periods, the Company generally utilizes the estimated annual effective tax rate method which involves the use of forecasted information. Under this method, the provision is calculated by applying an estimate of the annual effective tax rate for the full fiscal year to “ordinary” income or loss (pretax income or loss excluding unusual or infrequently occurring discrete items) for the reporting period. Jurisdictions with tax assets for which the Company believes a tax benefit cannot be realized are excluded from the computation of its annual effective tax rate. The Company’s effective tax rate changed to 65.7% for the three months ended September 30, 2017 , compared to 1,190.3% for the three months ended September 30, 2016 . The Company’s effective tax rate changed to (107.5)% for the nine months ended September 30, 2017 , compared to (2,564.1)% for the nine months ended September 30, 2016 . The change in rate for both reporting periods was primarily attributable to excluding the tax benefits associated with the Company’s U.S. jurisdiction due to the partial valuation allowance recorded against its domestic DTAs as of September 30, 2017 , and the year-to-date tax impact associated with intra-entity asset transfers. The effective tax rates for the three and nine months ended September 30, 2016 include the retroactive adoption of ASU 2016-09. The Company generated significant domestic DTAs in the year ended December 31, 2016 and nine month period ended September 30, 2017, primarily due to the significant excess tax benefits from stock option exercises and vesting of restricted stock upon application of ASU 2016-09 in the third quarter September 30, 2016. The Company assessed its ability to realize the benefits of its domestic DTAs prior to expiration by evaluating all available positive and negative evidence, objective and subjective in nature, including (1) cumulative results of operations in recent years, (2) sources of recent pre-tax losses, (3) estimates of future taxable income, (4) the length of net operating loss (“NOL”) carryforward periods, and (5) the ability to carry back losses to prior years. The Company determined it would be in a three-year cumulative taxable income position, had it not been for the impact of excess tax deductions from stock-based compensation under ASU 2016-09, and attributes recent period operating losses to operating expenses incurred to invest in the future growth of the business. The Company also measured its current DTA balances against estimates of future income based on objectively verifiable operating results from the Company’s recent history, as well as estimates of future income that incorporates the Company’s forecasted operating results for fiscal 2017. Due to the significant amount of additional stock-based compensation excess tax deductions available upon adoption of ASU 2016-9, the Company could not conclude, at the required more-likely-than-not level of certainty, that sufficient taxable income will be generated to realize the full benefit of its domestic DTAs as of September 30, 2017 prior to expiration. As such, a partial valuation allowance was recorded against the Company’s domestic DTAs as of September 30, 2017 in the amount of $18.6 million , which was approximately the same amount as the stock-based compensation excess tax benefits created during the nine months ended September 30, 2017 . The Company will continue to closely monitor the need for an additional valuation allowance against its existing domestic DTAs and any additional DTAs that are generated in each subsequent reporting period, which can be impacted by actual operating results compared to the Company’s forecast. Consistent with prior periods, the Company maintained a full valuation allowance against its California and Canada DTAs as of September 30, 2017 .

Net Income (Loss) per Share

Net Income (Loss) per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income (Loss) per Share	11. Net Income (Loss) per Share The Company’s basic net income (loss) per share is calculated by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. The diluted net income (loss) per share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. For purposes of this calculation, options to purchase common stock, restricted stock, restricted stock units and stock sold through the Company’s employee stock purchase plan are considered common stock equivalents. A reconciliation of the numerator and denominator used in the calculation of the basic and diluted income (loss) per share for the three and nine months ended September 30, 2017 and 2016 is as follows (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net income (loss) per share: Numerator Net income (loss)—basic and diluted $ 238 $ 11,906 $ (4,426 ) $ 17,210 Denominator Weighted average shares used to compute net income (loss) —Basic 33,446,841 30,604,384 32,766,135 30,269,463 Potential dilutive stock-based awards, as calculated using treasury stock method 2,217,431 3,150,999 — 3,098,155 Weighted average shares used to compute income (loss) —Diluted 35,664,272 33,755,383 32,766,135 33,367,618 Net income (loss) per share from: Basic $ 0.01 $ 0.39 $ (0.14 ) $ 0.57 Diluted $ 0.01 $ 0.35 $ (0.14 ) $ 0.52 Outstanding stock-based awards of 21,150 and 166,950 shares for the three months ended September 30, 2017 and 2016 , respectively, and 3.0 million and 199,450 shares for the nine months ended September 30, 2017 and 2016 , respectively, were excluded from the computation of diluted net income (loss) per share because their effect would have been anti-dilutive.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Commitments and Contingencies, Policy [Policy Text Block]	Contingent Consideration Certain agreements the Company enters into, including business combinations and licensing agreements, involve the potential payment of future consideration that is contingent upon certain performance and revenue milestones being achieved. Contingent consideration related to business combinations is recorded at the acquisition date at fair value and is remeasured each reporting period with the change in fair value recognized within sales, general and administrative expense in the consolidated statements of operations and comprehensive income . As of September 30, 2017 , the Company’s contingent consideration related to the acquisition of Crossmed and intangible assets through a licensing agreement. For more information with respect to the fair value of contingent consideration, refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ,” respectively.
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated balance sheet as of September 30, 2017 , the condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 , and the condensed consolidated statements of cash flows for the nine months ended September 30, 2017 and 2016 are unaudited. The unaudited condensed consolidated financial statements included herein have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and the applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. The condensed consolidated balance sheet as of December 31, 2016 was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company’s financial position as of September 30, 2017 , the results of its operations for the three and nine months ended September 30, 2017 and 2016 , and the cash flows for the nine months ended September 30, 2017 and 2016 . The results for the three and nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 or for any other future annual or interim period. Certain changes in presentation were made in the condensed consolidated financial statements for the three and nine months ended September 30, 2016 , to conform to the presentation for the three and nine months ended September 30, 2017 . The Company elected to early adopt Accounting Standards Update ( “ ASU ” ) 2016-09 in the fourth quarter of 2016 which requires the Company to reflect any adjustments as of January 1, 2016, the beginning of the annual period that includes the interim period of adoption. The impact of adoption was the creation of deferred tax assets (“DTAs”) in the balance sheet and recognition of excess tax benefits in our provision for (benefit from) income taxes rather than paid-in capital for all periods in fiscal year 2016. The Company elected to apply the presentation requirements for cash flows related to excess tax benefits retrospectively to all periods presented. Adoption of the new standard resulted in adjustments to our 2016 unaudited selected financial data previously reported in our Quarterly Report on Form 10-Q as follows: September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Balance Sheet Data: Prepaid expenses and other current assets $ 18,665 $ 19,209 Total current assets 267,223 267,767 Deferred taxes 13,394 22,059 Total assets 297,279 306,488 Other non-current liabilities 6,081 5,540 Total liabilities 43,425 42,884 Additional paid-in-capital 275,031 267,429 Accumulated deficit (17,616 ) (264 ) Total stockholders ’ equity 253,854 263,604 Total liabilities and stockholders ’ equity 297,279 306,488 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2016 (In thousands, except per share amounts) As Previously Reported As Adjusted As Previously Reported As Adjusted Condensed Consolidated Statements of Operations Data: Provision for (benefit from) income taxes $ 14 $ (12,998 ) $ 787 $ (16,564 ) Net (loss) income $ (1,106 ) $ 11,906 $ (141 ) $ 17,210 Net (loss) income per share: Basic $ (0.04 ) $ 0.39 $ 0.00 $ 0.57 Diluted $ (0.04 ) $ 0.35 $ 0.00 $ 0.52 Weighted average shares used to compute net (loss) income per share attributable to common stockholders: Basic 30,604,384 30,604,384 30,269,463 30,269,463 Diluted 30,604,384 33,755,383 30,269,463 33,367,618 Nine Months Ended September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Statement of Cash Flow Data: Net cash used in operating activities $ (10,051 ) $ (2,450 ) Net cash provided by financing activities $ 12,253 $ 4,652 The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2016 , included in the Company’s Annual Report on Form 10-K. During the nine months ended September 30, 2017 , the Company added accounting policies for goodwill, contingent consideration, intangible assets and non-marketable equity investments as described below. There have been no other changes to the Company’s significant accounting policies during the nine months ended September 30, 2017 , as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 . The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and equity accounts; disclosure of contingent assets and liabilities at the date of the financial statements; and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, including those related to marketable investments, provisions for doubtful accounts, sales return reserve, warranty reserve, valuation of inventories, useful lives of property and equipment, income taxes, and contingencies, among others. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other data. Actual results could differ from those estimates.
Goodwill	Goodwill Goodwill represents the excess of the purchase price of an acquired business or assets over the fair value of the identifiable assets acquired and liabilities assumed. Goodwill is not amortized, but is tested for impairment at least annually, or more frequently if events or circumstances indicate the carrying value may no longer be recoverable and that an impairment loss may have occurred. The Company continues to operate as one segment, which is considered to be the sole reporting unit, and therefore goodwill is tested for impairment at the consolidated level. As of September 30, 2017 , the Company’s goodwill is related to the acquisition of Crossmed S.p.a (“Crossmed”) during the third quarter of 2017 . Refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ” for more information.
Intangible Assets	Intangible Assets Intangible assets consist of intangibles acquired through a licensing arrangement and the acquisition of Crossmed during the third quarter of 2017. Indefinite-lived intangible assets relate to payments and future milestone payments, which are probable and estimable, for an exclusive right to licensed technology. The acquired licensed technology is accounted for as an indefinite-lived intangible asset until it reaches technological feasibility, which is determined on the basis of obtaining regulatory approval to market and commercialize the underlying products. Upon the commercialization of the underlying product, the capitalized amount will be amortized over its estimated useful life. Indefinite-lived intangible assets will be tested for impairment at least annually, or more frequently if events or circumstances indicate their carrying value may no longer be recoverable and that an impairment loss may have occurred. Finite-lived intangible assets are amortized using the straight-line method over the estimated economic useful lives of the assets, which is the period during which expected cash flows support the fair value of such intangible assets. The Company will review finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When such an event occurs, management will determine whether there has been impairment by comparing the anticipated undiscounted future net cash flows to the related asset group’s carrying value. If an asset is considered impaired, the asset will be written down to the determined fair value based on discounted cash flows. Refer to Note “ 6. Goodwill and Intangible Assets ” for more information on the Company’s intangible assets.
Non-Marketable Equity Investments	Non-Marketable Equity Investments Entities in which the Company has at least a 20% , but not more than a 50% , interest are accounted for under the equity method unless it is determined that the Company has a controlling financial interest in the entity, in which case the entity would be consolidated. Non-marketable equity investments are classified as investments and included in other non-current assets on the condensed consolidated balance sheet . The Company’s proportionate share of the operating results of its non-marketable equity method investments are recorded as profit or loss and included as a component of other expense, net, in the condensed consolidated statements of operations and comprehensive income . See Note “ 3. Investments and Fair Value of Financial Instruments ” for further details.
Segments	Segments The Company determined its operating segment on the same basis that it uses to evaluate its performance internally. The Company has one business activity: the design, development, manufacturing and marketing of innovative devices, and operates as one operating segment. The Company’s chief operating decision-maker, its Chief Executive Officer, reviews its operating results for the purpose of allocating resources and evaluating financial performance. The Company assigns revenue to a geographic area based on the destination to which it ships its products.
Recent Accounting Guidance	Recent Accounting Guidance Recently Adopted Accounting Standards In July 2015, the Financial Accounting Standards Board ( “ FASB ”) issued ASU No. 2015-11, Simplifying the Measurement of Inventory , which requires an entity to measure most inventory at the lower of cost and net realizable value, thereby simplifying the current guidance under which an entity must measure inventory at the lower of cost or market. In January 2017, the Company adopted the standard on a prospective basis and the adoption did not have a material impact on its financial position. Recently Issued Accounting Standards In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which outlines a comprehensive new revenue recognition model designed to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers — Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which further clarifies the implementation guidance on principal versus agent considerations contained in ASU No. 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers — Identifying Performance Obligations and Licensing , which further clarifies the implementation guidance relating to identifying performance obligations and the licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers — Narrow-Scope improvements and Practical Expedients , which further clarifies the implementation on narrow scope improvements and practical expedients. In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606 — Revenue from Contracts with Customer s , which makes minor corrections or minor improvements to the Codification related to ASU No. 2014-09 that are not expected to have a significant effect on the Company ’ s current accounting practice. In September 2017, the FASB issued ASU No. 2017-13, Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842): Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments , (“ASU No. 2017-13”) which provides additional clarification and implementation guidance on the previously issued ASU No. 2014-09. These standards will be effective for the Company in the first quarter of 2018 pursuant to ASU No. 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date , issued by the FASB in August 20 15. The Company intends to adopt the new standard on a modified retrospective basis on January 1, 2018. Under this method, the C ompany will record a cumulative-effect adjustment to the opening balance of retained earnings in the initial year of adoption. The timing of revenue recognition based on the guidance related to transfer of control may result in acceleration of revenue recognition for some contracts. The Company does not expect the impact of the new standard to be material, but it expands financial statement disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. As we continue our assessment through the remainder of 2017, our preliminary assessment is subject to change. In February 2016, the FASB issued ASU No. 2016-02, Leases, which amends the existing accounting standards for leases. In September 2017, the FASB issued ASU No. 2017-13 which provides additional clarification and implementation guidance on the previously issued ASU No. 2016-02. Under the new guidance, a lessee will be required to recognize a lease liability and right-of-use asset for all leases with terms in excess of twelve months. The new guidance also modifies the classification criteria and accounting for sales-type and direct financing leases, and requires additional disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. Consistent with current guidance, a lessee’s recognition, measurement, and presentation of expenses and cash flows arising from a lease will continue to depend primarily on its classification. The accounting standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and must be applied using a modified retrospective approach. Early adoption is permitted. While the Company is continuing to assess all potential impacts of the standard, it expects that most of its lease commitments will be subject to the updated standard and recognized as lease liabilities and right-of-use assets upon adoption. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses . The standard changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The Company will recognize an allowance for credit losses on available-for-sale securities rather than deductions in amortized cost. The standard is effective for fiscal years and interim periods beginning after December 15, 2019. Early adoption is permitted for all periods beginning after December 15, 2018. The Company is currently evaluating the impact of adopting this standard. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows: Restricted Cash , a consensus of the FASB Emerging Issues Task Force . The standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling the total beginning and end of period amounts shown on the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. The Company does not expect the adoption of ASU 2016-18 to have a material impact on its consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation - Scope of Modification Accounting. The standard provides clarification on when modification accounting should be used for changes to the terms or conditions of a share-based payment award. This standard does not change the accounting for modifications but clarifies that modification accounting guidance should only be applied if there is a change to the value, vesting conditions, or award classification and would not be required if the changes are considered non-substantive. The standard is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. Early adoption is permitted. The guidance will be applied prospectively upon adoption. The Company does not expect the adoption of ASU 2017-09 to have a material impact on its consolidated financial statements, however the impact to share-based compensation expense will depend on the terms specified in any new changes to share-based payment awards subsequent to the adoption.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Adoption of the new standard resulted in adjustments to our 2016 unaudited selected financial data previously reported in our Quarterly Report on Form 10-Q as follows: September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Balance Sheet Data: Prepaid expenses and other current assets $ 18,665 $ 19,209 Total current assets 267,223 267,767 Deferred taxes 13,394 22,059 Total assets 297,279 306,488 Other non-current liabilities 6,081 5,540 Total liabilities 43,425 42,884 Additional paid-in-capital 275,031 267,429 Accumulated deficit (17,616 ) (264 ) Total stockholders ’ equity 253,854 263,604 Total liabilities and stockholders ’ equity 297,279 306,488 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2016 (In thousands, except per share amounts) As Previously Reported As Adjusted As Previously Reported As Adjusted Condensed Consolidated Statements of Operations Data: Provision for (benefit from) income taxes $ 14 $ (12,998 ) $ 787 $ (16,564 ) Net (loss) income $ (1,106 ) $ 11,906 $ (141 ) $ 17,210 Net (loss) income per share: Basic $ (0.04 ) $ 0.39 $ 0.00 $ 0.57 Diluted $ (0.04 ) $ 0.35 $ 0.00 $ 0.52 Weighted average shares used to compute net (loss) income per share attributable to common stockholders: Basic 30,604,384 30,604,384 30,269,463 30,269,463 Diluted 30,604,384 33,755,383 30,269,463 33,367,618 Nine Months Ended September 30, 2016 (In thousands) As Previously Reported As Adjusted Condensed Consolidated Statement of Cash Flow Data: Net cash used in operating activities $ (10,051 ) $ (2,450 ) Net cash provided by financing activities $ 12,253 $ 4,652

Investments and Fair Value of19

Investments and Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Schedule of Marketable Investments	Marketable Investments The Company’s marketable investments have been classified and accounted for as available-for-sale. The Company’s marketable investments as of September 30, 2017 and December 31, 2016 were as follows (in thousands): September 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 23,471 $ 2 $ (1 ) $ 23,472 U.S. Treasury 9,004 — (4 ) 9,000 U.S. agency and government sponsored securities 3,600 — (8 ) 3,592 U.S. states and municipalities 10,207 1 (4 ) 10,204 Corporate bonds 106,964 48 (77 ) 106,935 Total $ 153,246 $ 51 $ (94 ) $ 153,203 December 31, 2016 Amortized Cost Gross Gross Fair Value Commercial paper $ 4,237 $ 1 $ — $ 4,238 U.S. Treasury 4,996 — — 4,996 U.S. agency and government sponsored securities 8,803 3 (12 ) 8,794 U.S. states and municipalities 27,429 1 (75 ) 27,355 Corporate bonds 69,009 36 (120 ) 68,925 Non-U.S. government debt securities 1,209 — — 1,209 Total $ 115,683 $ 41 $ (207 ) $ 115,517
Schedule of the Fair Value of Marketable Investments in an Unrealized Loss Position for Less than Twelve Months	The following tables present the gross unrealized losses and the fair value for those marketable investments that were in an unrealized loss position for less than and more than twelve months as of September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 Less than 12 months 12 months or more Total Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Commercial paper $ 10,959 $ (1 ) $ — $ — $ 10,959 $ (1 ) U.S. Treasury 9,000 (4 ) — — 9,000 (4 ) U.S. agency and government sponsored securities 1,600 — 1,992 (8 ) 3,592 (8 ) U.S. states and municipalities 7,184 (4 ) — — 7,184 (4 ) Corporate bonds 49,655 (48 ) 4,168 (29 ) 53,823 (77 ) Total $ 78,398 $ (57 ) $ 6,160 $ (37 ) $ 84,558 $ (94 ) December 31, 2016 Less than 12 months Fair Value Gross Unrealized Losses U.S. agency and government sponsored securities $ 3,291 $ (12 ) U.S. states and municipalities 22,286 (75 ) Corporate bonds 29,748 (120 ) Total $ 55,325 $ (207 )
Schedule of Contractual Maturities of Marketable Investments	The contractual maturities of the Company’s marketable investments as of September 30, 2017 and December 31, 2016 were as follows (in thousands): September 30, December 31, 2016 Fair Value Fair Value Due in less than one year $ 122,829 $ 71,051 Due in one to five years 30,374 44,466 Total $ 153,203 $ 115,517
Schedule of Fair Value of Assets and Liabilities	The following table sets forth the Company’s financial assets measured at fair value by level within the fair value hierarchy (in thousands): As of September 30, 2017 Level 1 Level 2 Total Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 9,084 $ 9,084 Money market funds 9,042 — 9,042 U.S. Treasury — — — U.S. states and municipalities — 6,500 6,500 Marketable investments: Commercial paper — 23,472 23,472 U.S. Treasury 9,000 — 9,000 U.S. agency and government sponsored securities — 3,592 3,592 U.S. states and municipalities — 10,204 10,204 Corporate bonds — 106,935 106,935 Total $ 18,042 $ 159,787 $ 177,829 As of December 31, 2016 Level 1 Level 2 Total Fair Value Financial Assets Cash equivalents: Money market funds $ 873 $ — $ 873 Marketable investments: Commercial paper — 4,238 4,238 U.S. Treasury 4,996 — 4,996 U.S. agency and government sponsored securities — 8,794 8,794 U.S. states and municipalities — 27,355 27,355 Corporate bonds — 68,925 68,925 Non-U.S. government debt securities — 1,209 1,209 Total $ 5,869 $ 110,521 $ 116,390 During the nine months ended September 30, 2017 and 2016 , the Company did not record impairment charges related to its marketable investments and the Company did not hold any Level 3 marketable investments as of September 30, 2017 or December 31, 2016 . In addition to the amounts presented above, the Company recorded contingent consideration liabilities at fair value during 2017. During the three months ended September 30, 2017, the Company acquired Crossmed and recorded contingent consideration in the amount of $4.3 million . Also during the three months ended September 30, 2017, the Company entered into an exclusive technology license agreement and recorded contingent consideration in the amount of $12.7 million . These contingent consideration liabilities are classified as Level 3 measurements for which fair value is derived from significant unobservable inputs, such as projected revenue and estimates in the timing and likelihood of achieving revenue-based milestones. During the three months ended September 30, 2017 , there were no changes in fair value for these contingent consideration liabilities . For more information with respect to the fair value of contingent consideration, refer to Note “ 5. Business Combination ” and Note “ 6. Goodwill and Intangible Assets ,” respectively. During the nine months ended September 30, 2017 and 2016 , the Company did not have any transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy. Additionally, the Company did not have any financial assets and liabilities measured at fair value on a non-recurring basis as of September 30, 2017 or December 31, 2016 .

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	The following table shows the components of prepaid expenses and other current assets as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Prepaid tax $ 1,023 $ 4,656 Prepaid expenses 5,213 4,573 Other current assets 8,228 9,498 Prepaid expenses and other current assets $ 14,464 $ 18,727
Schedule of Inventories	The following table shows the components of inventories as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Raw materials $ 11,288 $ 11,367 Work in process 6,923 3,663 Finished goods 72,318 57,982 Inventories $ 90,529 $ 73,012
Schedule of Accrued Liabilities	The following table shows the components of accrued liabilities as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Payroll and employee-related cost $ 22,244 $ 16,956 Sales return reserve 3,024 2,753 Preclinical and clinical trial cost 1,501 2,054 Royalty 946 802 Product warranty 1,066 1,254 Leasehold improvement expenditures 2,904 260 Acquisition-related liabilities 1 3,514 — Other accrued liabilities 10,113 7,611 Total accrued liabilities $ 45,312 $ 31,690
Schedule of Estimated Product Warranty Accrual	The following table shows the changes in the Company’s estimated product warranty accrual, included in accrued liabilities, as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Balance at the beginning of the period $ 1,254 $ 713 Accruals of warranties issued 289 1,176 Settlements of warranty claims (477 ) (635 ) Balance at the end of the period $ 1,066 $ 1,254
Schedule of Other Non-Current Liabilities	The following table shows the components of other non-current liabilities as of September 30, 2017 and December 31, 2016 (in thousands): September 30, December 31, Deferred tax liabilities $ 3,299 $ 824 Licensing-related cost 1 12,717 — Other non-current liabilities 2,101 — Total other non-current liabilities $ 18,117 $ 824 1 Amount relates to the liability recorded for probable future milestone payments to be made under the licensing agreement described in Note “ 6. Goodwill and Intangible Assets ,” refer therein for more information.

Business Combination (Tables)

Business Combination (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Business Acquisition Consideration Transferred	The following table summarizes the Closing Date fair value of the consideration transferred (in thousands): Cash, net of working capital and financial debt adjustments $ 9,918 Fair value of contingent consideration for milestone payments 4,343 Contract purchase price $ 14,261 Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra 3,273 Total value of consideration transferred $ 17,534
Schedule of Purchase Price Allocation	The following table presents the preliminary allocation of the purchase price for Crossmed (in thousands): Acquisition-Date Fair Value Estimated Useful Life of Finite-Lived Intangible Assets Tangible assets acquired and (liabilities) assumed: Accounts receivable $ 4,406 Inventories 1,343 Other current and non-current assets 1,316 Property and equipment, net 829 Accounts payable (740 ) Accrued liabilities and obligations for short-term debt and credit facilities (2,164 ) Deferred tax liabilities (2,472 ) Other non-current liabilities (797 ) Intangible assets acquired: Customer relationships $ 6,790 15 years Other 1,750 5 years Goodwill 7,273 Total purchase price $ 17,534
Pro Forma Information	he unaudited pro forma information is presented below (unaudited, in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Pro forma net revenue $ 83,911 $ 68,012 $ 240,506 $ 193,521 Pro forma net income (loss) 238 11,950 (4,695 ) 17,020

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill	The following table presents the changes in goodwill during the nine months ended September 30, 2017 (in thousands): Total Company Balance as of December 31, 2016 $ — Acquisition of Crossmed (1) 7,273 Foreign currency translation 176 Balance as of September 30, 2017 $ 7,449 1 Goodwill includes a $2.5 million adjustment for the relative impact of recording the deferred tax liability associated with the acquired intangible assets of Crossmed. Refer to Note “ 5. Business Combination ” for more information.
Schedule of finite-lived intangible assets	The following table presents details of the Company’s acquired definite-lived and indefinite-lived intangible assets (in thousands, except weighted-average amortization period): As of September 30, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15 years $ 7,044 $ (168 ) $ 6,876 Other 5 years 1,815 (87 ) 1,728 Total intangible assets subject to amortization $ 8,859 $ (255 ) $ 8,604 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,076 $ (255 ) $ 23,821 The total intangible assets subject amortization relate to the acquisition of Crossmed during the third quarter of 2017. During both the three and nine months ended September 30, 2017 , the Company recorded amortization expense of $0.3 million in sales, general and administrative expense related to the Company’s finite-lived intangible assets . Refer to Note “ 5. Business Combination ” for more information.
Schedule of indefinite-lived intangible assets	The following table presents details of the Company’s acquired definite-lived and indefinite-lived intangible assets (in thousands, except weighted-average amortization period): As of September 30, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15 years $ 7,044 $ (168 ) $ 6,876 Other 5 years 1,815 (87 ) 1,728 Total intangible assets subject to amortization $ 8,859 $ (255 ) $ 8,604 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,076 $ (255 ) $ 23,821 The total intangible assets subject amortization relate to the acquisition of Crossmed during the third quarter of 2017. During both the three and nine months ended September 30, 2017 , the Company recorded amortization expense of $0.3 million in sales, general and administrative expense related to the Company’s finite-lived intangible assets . Refer to Note “ 5. Business Combination ” for more information.

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity	Activity of stock options under the Penumbra, Inc. 2005 Stock Plan, the Penumbra, Inc. 2011 Equity Incentive Plan and the Amended and Restated Penumbra, Inc. 2014 Equity Incentive Plan (collectively the “Plans”) during the nine months ended September 30, 2017 is set forth below: Number of Shares Weighted-Average Exercise Price Balance at December 31, 2016 2,876,955 $ 14.63 Options exercised (678,825 ) 6.21 Options canceled (2,866 ) 16.98 Balance at September 30, 2017 2,195,264 17.24
Summary of Unvested Restricted Stock and Restricted Stock Unit Activity	Activity of unvested restricted stock and restricted stock units under the Plans during the nine months ended September 30, 2017 is set forth below: Number of Shares Weighted -Average Grant Date Fair Value Unvested at December 31, 2016 1,002,944 $ 29.44 Granted 99,638 80.04 Vested (325,023 ) 24.79 Canceled/Forfeited (20,687 ) 45.22 Unvested and expected to vest at September 30, 2017 756,872 37.67
Schedule of Stock-based Compensation Expense	The following table sets forth the stock-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of revenue $ 316 $ 83 $ 817 $ 742 Research and development 352 251 913 790 Sales, general and administrative 3,819 3,930 11,362 9,268 Total $ 4,487 $ 4,264 $ 13,092 $ 10,800

Accumulated Other Comprehensi24

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (105 ) $ (4,583 ) $ (4,688 ) $ (163 ) $ (1,952 ) $ (2,115 ) Other comprehensive income before reclassifications: Unrealized gains —marketable investments 157 — 157 401 — 401 Foreign currency translation gains (losses) — 5,771 5,771 — (1,732 ) (1,732 ) Income tax effect — (expense) benefit — — — (145 ) 1 (144 ) Net of tax 157 5,771 5,928 256 (1,731 ) (1,475 ) Amounts reclassified from accumulated other comprehensive income to earnings: Realized gains — marketable investments (36 ) — (36 ) (3 ) — (3 ) Income tax effect — benefit — — — 1 — 1 Net of tax (36 ) — (36 ) (2 ) — (2 ) Net current-year other comprehensive income (loss) 121 5,771 5,892 254 (1,731 ) (1,477 ) Balance at end of the period $ 16 $ 1,188 $ 1,204 $ 91 $ (3,683 ) $ (3,592 ) The following table summarizes the changes in the accumulated balances during the three and nine months ended September 30, 2017 and 2016 , and includes information regarding the manner in which the reclassifications out of accumulated other comprehensive income (loss) into earnings affect the Company’s condensed consolidated statements of operations and comprehensive income (in thousands): Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (38 ) $ (4,657 ) $ (4,695 ) $ 206 $ (2,785 ) $ (2,579 ) Other comprehensive income before reclassifications: Unrealized gains (losses) — marketable investments 54 — 54 (178 ) — (178 ) Foreign currency translation gains (losses) — 5,845 5,845 — (901 ) (901 ) Income tax effect — benefit — — — 63 3 66 Net of tax 54 5,845 5,899 (115 ) (898 ) (1,013 ) Amounts reclassified from accumulated other comprehensive income to earnings: Realized losses — marketable investments — — — 1 — 1 Income tax effect — expense — — — (1 ) — (1 ) Net of tax — — — — — — Net current-year other comprehensive income (loss) 54 5,845 5,899 (115 ) (898 ) (1,013 ) Balance at end of the period $ 16 $ 1,188 $ 1,204 $ 91 $ (3,683 ) $ (3,592 )

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Reconciliation of the Numerator and Denominator used in the Calculation of the Basic and Diluted Earnings per Share	A reconciliation of the numerator and denominator used in the calculation of the basic and diluted income (loss) per share for the three and nine months ended September 30, 2017 and 2016 is as follows (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net income (loss) per share: Numerator Net income (loss)—basic and diluted $ 238 $ 11,906 $ (4,426 ) $ 17,210 Denominator Weighted average shares used to compute net income (loss) —Basic 33,446,841 30,604,384 32,766,135 30,269,463 Potential dilutive stock-based awards, as calculated using treasury stock method 2,217,431 3,150,999 — 3,098,155 Weighted average shares used to compute income (loss) —Diluted 35,664,272 33,755,383 32,766,135 33,367,618 Net income (loss) per share from: Basic $ 0.01 $ 0.39 $ (0.14 ) $ 0.57 Diluted $ 0.01 $ 0.35 $ (0.14 ) $ 0.52

Organization and Description 26

Organization and Description of Business (Details)	9 Months Ended
	Sep. 30, 2017market
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of major markets	2

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Additional Disclosures (Details)	9 Months Ended
	Sep. 30, 2017segmentactivity
Schedule of Equity Method Investments [Line Items]
Number of business activities | activity	1
Number of Operating Segments | segment	1
Minimum
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	20.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	50.00%

Summary of Significant Accoun28

Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2016USD ($)$ / sharesshares	Sep. 30, 2017USD ($)segment$ / sharesshares	Sep. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of Operating Segments | segment			1
Condensed Consolidated Balance Sheet Data:
Prepaid expenses and other current assets	$ 14,464		$ 14,464		$ 18,727
Total current assets	371,781		371,781		263,827
Deferred taxes	22,503		22,503		22,476
Assets	459,094		459,094		308,254
Other non-current liabilities	18,117		18,117		824
Liabilities	75,262		75,262		41,707
Additional paid-in capital	389,682		389,682		273,865
Accumulated deficit	(7,087)		(7,087)		(2,661)
Total stockholder’ equity	383,832		383,832		266,547
Liabilities and Equity	459,094		459,094		$ 308,254
Condensed Consolidated Statements of Operations Data:
Provision for (benefit from) income taxes	456	$ (12,998)	2,293	$ (16,564)
Net (loss) income	$ 238	$ 11,906	$ (4,426)	$ 17,210
Net (loss) income per share:
Basic (in dollars per share) | $ / shares	$ 0.01	$ 0.39	$ (0.14)	$ 0.57
Diluted (in dollars per share) | $ / shares	$ 0.01	$ 0.35	$ (0.14)	$ 0.52
Weighted average shares used to compute net (loss) income per share attributable to common stockholders:
Basic (in shares) | shares	33,446,841	30,604,384	32,766,135	30,269,463
Diluted (in shares) | shares	35,664,272	33,755,383	32,766,135	33,367,618
Condensed Consolidated Statement of Cash Flow Data:
Net cash (used in) operating activities			$ 13,598	$ (2,450)
Net cash (used in) financing activities			$ 101,914	4,652
Accounting Standards Update 2016-09
Condensed Consolidated Balance Sheet Data:
Prepaid expenses and other current assets		$ 19,209		19,209
Total current assets		267,767		267,767
Deferred taxes		22,059		22,059
Assets		306,488		306,488
Other non-current liabilities		5,540		5,540
Liabilities		42,884		42,884
Additional paid-in capital		267,429		267,429
Accumulated deficit		(264)		(264)
Total stockholder’ equity		263,604		263,604
Liabilities and Equity		306,488		306,488
Condensed Consolidated Statements of Operations Data:
Provision for (benefit from) income taxes		(12,998)		(16,564)
Net (loss) income		$ 11,906		$ 17,210
Net (loss) income per share:
Basic (in dollars per share) | $ / shares		$ 0.39		$ 0.57
Diluted (in dollars per share) | $ / shares		$ 0.35		$ 0.52
Weighted average shares used to compute net (loss) income per share attributable to common stockholders:
Basic (in shares) | shares		30,604,384		30,269,463
Diluted (in shares) | shares		33,755,383		33,367,618
Condensed Consolidated Statement of Cash Flow Data:
Net cash (used in) operating activities				$ (2,450)
Net cash (used in) financing activities				4,652
As Previously Reported
Condensed Consolidated Balance Sheet Data:
Prepaid expenses and other current assets		$ 18,665		18,665
Total current assets		267,223		267,223
Deferred taxes		13,394		13,394
Assets		297,279		297,279
Other non-current liabilities		6,081		6,081
Liabilities		43,425		43,425
Additional paid-in capital		275,031		275,031
Accumulated deficit		(17,616)		(17,616)
Total stockholder’ equity		253,854		253,854
Liabilities and Equity		297,279		297,279
Condensed Consolidated Statements of Operations Data:
Provision for (benefit from) income taxes		14		787
Net (loss) income		$ (1,106)		$ (141)
Net (loss) income per share:
Basic (in dollars per share) | $ / shares		$ (0.04)		$ 0
Diluted (in dollars per share) | $ / shares		$ (0.04)		$ 0
Weighted average shares used to compute net (loss) income per share attributable to common stockholders:
Basic (in shares) | shares		30,604,384		30,269,463
Diluted (in shares) | shares		30,604,384		30,269,463
Condensed Consolidated Statement of Cash Flow Data:
Net cash (used in) operating activities				$ (10,051)
Net cash (used in) financing activities				$ 12,253

Investments and Fair Value of29

Investments and Fair Value of Financial Instruments - Gains and Losses of Marketable Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 153,246	$ 115,683
Gross Unrealized Gains	51	41
Gross Unrealized Losses	(94)	(207)
Fair Value	153,203	115,517
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,471	4,237
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(1)	0
Fair Value	23,472	4,238
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,004	4,996
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4)	0
Fair Value	9,000	4,996
U.S. agency and government sponsored securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,600	8,803
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(8)	(12)
Fair Value	3,592	8,794
U.S. states and municipalities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,207	27,429
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(4)	(75)
Fair Value	10,204	27,355
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	106,964	69,009
Gross Unrealized Gains	48	36
Gross Unrealized Losses	(77)	(120)
Fair Value	$ 106,935	68,925
Non-U.S. government debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,209
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		$ 1,209

Investments and Fair Value of30

Investments and Fair Value of Financial Instruments - Marketable Securities in an Unrealized Loss Position (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	$ 78,398,000	$ 55,325,000
Less than 12 months: Gross Unrealized Losses	(57,000)	(207,000)
12 Months of more: Fair Value	6,160,000
12 months or more: Gross Unrealized Losses	(37,000)	0
Total: Fair Value	84,558,000
Total: Gross Unrealized Losses	(94,000)
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	10,959,000
Less than 12 months: Gross Unrealized Losses	(1,000)
12 Months of more: Fair Value	0
12 months or more: Gross Unrealized Losses	0
Total: Fair Value	10,959,000
Total: Gross Unrealized Losses	(1,000)
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	9,000,000
Less than 12 months: Gross Unrealized Losses	(4,000)
12 Months of more: Fair Value	0
12 months or more: Gross Unrealized Losses	0
Total: Fair Value	9,000,000
Total: Gross Unrealized Losses	(4,000)
U.S. agency and government sponsored securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	1,600,000	3,291,000
Less than 12 months: Gross Unrealized Losses	0	(12,000)
12 Months of more: Fair Value	1,992,000
12 months or more: Gross Unrealized Losses	(8,000)
Total: Fair Value	3,592,000
Total: Gross Unrealized Losses	(8,000)
U.S. states and municipalities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	7,184,000	22,286,000
Less than 12 months: Gross Unrealized Losses	(4,000)	(75,000)
12 Months of more: Fair Value	0
12 months or more: Gross Unrealized Losses	0
Total: Fair Value	7,184,000
Total: Gross Unrealized Losses	(4,000)
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	49,655,000	29,748,000
Less than 12 months: Gross Unrealized Losses	(48,000)	$ (120,000)
12 Months of more: Fair Value	4,168,000
12 months or more: Gross Unrealized Losses	(29,000)
Total: Fair Value	53,823,000
Total: Gross Unrealized Losses	$ (77,000)

Investments and Fair Value of31

Investments and Fair Value of Financial Instruments - Contractual Maturities of Marketable Investments (Details) $ in Thousands	Sep. 30, 2017USD ($)security	Dec. 31, 2016USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of securities in a loss position for more than twelve months | security	0
Due in less than one year	$ 122,829	$ 71,051
Due in one to five years	30,374	44,466
Total	$ 153,203	$ 115,517

Investments and Fair Value of32

Investments and Fair Value of Financial Instruments - Non-Marketable Equity Investments (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	May 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Carrying value of investment					$ 0
Net loss from equity investments		$ 703,000	$ 0
MVI
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage				50.00%
Carrying value of investment	$ 4,400,000	4,400,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	(1,100,000)	(1,400,000)
Parent Company [Member] | Other Expenses, net | MVI
Schedule of Equity Method Investments [Line Items]
Net loss from equity investments	$ (500,000)	$ (700,000)

Investments and Fair Value of33

Investments and Fair Value of Financial Instruments - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Licensing-related cost, Noncurrent	$ 12,717	$ 0
Recurring
Financial Assets
Total	177,829	116,390
Recurring | Commercial paper
Financial Assets
Marketable investments	23,472	4,238
Recurring | U.S. Treasury
Financial Assets
Marketable investments	9,000	4,996
Recurring | U.S. agency and government sponsored securities
Financial Assets
Marketable investments	3,592	8,794
Recurring | U.S. states and municipalities
Financial Assets
Marketable investments	10,204	27,355
Recurring | Corporate bonds
Financial Assets
Marketable investments	106,935	68,925
Recurring | Non-U.S. government debt securities
Financial Assets
Marketable investments		1,209
Recurring | Commercial paper
Financial Assets
Cash equivalents	9,084
Recurring | Money market funds
Financial Assets
Cash equivalents	9,042	873
Recurring | U.S. Treasury
Financial Assets
Cash equivalents	0
Recurring | U.S. states and municipalities
Financial Assets
Cash equivalents	6,500
Recurring | Level 1
Financial Assets
Total	18,042	5,869
Recurring | Level 1 | Commercial paper
Financial Assets
Marketable investments	0	0
Recurring | Level 1 | U.S. Treasury
Financial Assets
Marketable investments	9,000	4,996
Recurring | Level 1 | U.S. agency and government sponsored securities
Financial Assets
Marketable investments	0	0
Recurring | Level 1 | U.S. states and municipalities
Financial Assets
Marketable investments	0	0
Recurring | Level 1 | Corporate bonds
Financial Assets
Marketable investments	0	0
Recurring | Level 1 | Non-U.S. government debt securities
Financial Assets
Marketable investments		0
Recurring | Level 1 | Commercial paper
Financial Assets
Cash equivalents	0
Recurring | Level 1 | Money market funds
Financial Assets
Cash equivalents	9,042	873
Recurring | Level 1 | U.S. Treasury
Financial Assets
Cash equivalents	0
Recurring | Level 1 | U.S. states and municipalities
Financial Assets
Cash equivalents	0
Recurring | Level 2
Financial Assets
Total	159,787	110,521
Recurring | Level 2 | Commercial paper
Financial Assets
Marketable investments	23,472	4,238
Recurring | Level 2 | U.S. Treasury
Financial Assets
Marketable investments	0	0
Recurring | Level 2 | U.S. agency and government sponsored securities
Financial Assets
Marketable investments	3,592	8,794
Recurring | Level 2 | U.S. states and municipalities
Financial Assets
Marketable investments	10,204	27,355
Recurring | Level 2 | Corporate bonds
Financial Assets
Marketable investments	106,935	68,925
Recurring | Level 2 | Non-U.S. government debt securities
Financial Assets
Marketable investments		1,209
Recurring | Level 2 | Commercial paper
Financial Assets
Cash equivalents	9,084
Recurring | Level 2 | Money market funds
Financial Assets
Cash equivalents	0	$ 0
Recurring | Level 2 | U.S. Treasury
Financial Assets
Cash equivalents	0
Recurring | Level 2 | U.S. states and municipalities
Financial Assets
Cash equivalents	$ 6,500

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid tax	$ 1,023	$ 4,656
Prepaid expenses	5,213	4,573
Other current assets	8,228	9,498
Prepaid expenses and other current assets	$ 14,464	$ 18,727

Balance Sheet Components - Inve

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 11,288	$ 11,367
Work in process	6,923	3,663
Finished goods	72,318	57,982
Inventories	$ 90,529	$ 73,012

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Payroll and employee-related cost	$ 22,244	$ 16,956
Sales return reserve	3,024	2,753
Preclinical and clinical trial cost	1,501	2,054
Royalty	946	802
Product warranty	1,066	1,254
Leasehold improvement expenditures	2,904	260
Acquisition-related liabilities1	3,514	0
Other accrued liabilities	10,113	7,611
Total accrued liabilities	$ 45,312	$ 31,690

Balance Sheet Components - Prod

Balance Sheet Components - Product Warranty (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Product Warranty, Increase (Decrease) [Roll Forward]
Balance at the beginning of the period	$ 1,254	$ 713
Accruals of warranties issued	289	1,176
Settlements of warranty claims	(477)	(635)
Balance at the end of the period	$ 1,066	$ 1,254

Balance Sheet Components - Othe

Balance Sheet Components - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred tax liabilities	$ 3,299	$ 824
Licensing-related cost, Noncurrent	12,717	0
Other Accrued Liabilities, Noncurrent	2,101	0
Total other non-current liabilities	$ 18,117	$ 824

Business Combination - Narrati

Business Combination - Narrative (Details) € in Millions	Jul. 03, 2017EUR (€)	Jul. 03, 2017USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)segment	Sep. 30, 2016USD ($)
Business Acquisition [Line Items]
Number of Operating Segments | segment					1
Revenue			$ 83,911,000	$ 67,187,000	$ 237,713,000	$ 190,212,000
Net income (loss)			$ 238,000	$ 11,906,000	(4,426,000)	$ 17,210,000
Crossmed
Business Acquisition [Line Items]
Payments to acquire business	€ 8.2	$ 9,400,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Maximum Unlimited			0
Contingent consideration for milestone payments		4,343,000
Deferred Tax Liabilities, Net		$ 2,472,000	$ 2,500,000		2,500,000
Revenue			2,700,000		2,700,000
Net income (loss)			(300,000)		(300,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings			0
Current Liabilities | Crossmed
Business Acquisition [Line Items]
Contingent consideration for milestone payments			3,000,000		3,000,000
Noncurrent Liabilities | Crossmed
Business Acquisition [Line Items]
Contingent consideration for milestone payments			$ 1,300,000		$ 1,300,000

Business Combination - Consider

Business Combination - Consideration Transferred (Details) - Crossmed $ in Thousands	Jul. 03, 2017USD ($)
Business Acquisition [Line Items]
Purchase Consideration To Acquire Businesses Net Of Working Capital Adjustments Excluding Contingent Consideration	$ 9,918
Fair value of contingent consideration for milestone payments	4,343
Contract purchase price	14,261
Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra	3,273
Total value of consideration transferred	$ 17,534

Business Combination - Purchase

Business Combination - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Jul. 03, 2017	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill		$ 7,449	$ 0
Crossmed
Business Acquisition [Line Items]
Accounts receivable, net	$ 4,406
Inventories	1,343
Other current and non-current assets	1,316
Property and equipment, net	829
Accounts payable	(740)
Accrued liabilities and obligations for short-term debt and credit facilities	(2,164)
Deferred Tax Liabilities, Net	(2,472)	$ (2,500)
Other non-current liabilities	(797)
Goodwill	7,273
Total purchase price	17,534
Customer relationships
Business Acquisition [Line Items]
Estimated Useful Life of Finite-Lived Intangible Assets		15 years
Customer relationships | Crossmed
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 6,790
Estimated Useful Life of Finite-Lived Intangible Assets	15 years
Other
Business Acquisition [Line Items]
Estimated Useful Life of Finite-Lived Intangible Assets		5 years
Other | Crossmed
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 1,750
Estimated Useful Life of Finite-Lived Intangible Assets	5 years

Business Combination - Pro Form

Business Combination - Pro Forma (Details) - Crossmed - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue	$ 83,911	$ 68,012	$ 240,506	$ 193,521
Business Acquisition, Pro Forma Net Income (Loss)	$ 238	$ 11,950	$ (4,695)	$ 17,020

Goodwill and Intangible Asset43

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2016	$ 0
Acquisition of Crossmed(1)	7,273
Foreign currency translation and other adjustments	176
Balance as of September 30, 2017	$ 7,449

Goodwill and Intangible Asset44

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 300	$ 300
Finite lived intangible assets: gross carrying amount	8,859	8,859
Accumulated amortization	(255)	(255)
Finite lived intangible assets: net	8,604	8,604
Indefinite-lived intangible assets	15,217	15,217
Total intangible assets, gross	24,076	24,076
Total intangible assets, net	23,821	23,821		$ 0
Payments to acquire intangible assets	2,500	2,500	$ 0
Indefinite-lived license agreements	15,200	15,200
Licensing-related cost, Noncurrent	12,717	$ 12,717		$ 0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		15 years
Finite lived intangible assets: gross carrying amount	7,044	$ 7,044
Accumulated amortization	(168)	(168)
Finite lived intangible assets: net	6,876	$ 6,876
Other
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		5 years
Finite lived intangible assets: gross carrying amount	1,815	$ 1,815
Accumulated amortization	(87)	(87)
Finite lived intangible assets: net	$ 1,728	$ 1,728

Commitments and Contingencies -

Commitments and Contingencies - Lease and Purchase Commitments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 1.4	$ 1.4	$ 4.3	$ 3.8

Commitments and Contingencies46

Commitments and Contingencies - Royalty Obligations (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Cost of Sales
Other Commitments [Line Items]
Royalty expense	$ 1,000,000	$ 700,000	$ 3,000,000	$ 2,100,000
Royalty Agreement, March 2005
Other Commitments [Line Items]
Minimum annual royalty payments	$ 100,000		$ 100,000		$ 100,000
Royalty Agreement, April 2012
Other Commitments [Line Items]
Royalty as a percent of sales			5.00%
Royalty Agreement, November 2013, Less than $5 Million in Sales
Other Commitments [Line Items]
Royalty as a percent of sales			3.00%
Royalty Agreement, November 2013, Greater than $5 Million in Sales
Other Commitments [Line Items]
Royalty as a percent of sales			1.00%
Royalty threshold			$ 5,000,000
Royalty Agreement, April 2015
Other Commitments [Line Items]
Royalty as a percent of sales			2.00%

Stockholder's Equity - Common S

Stockholder's Equity - Common Stock (Details) - Underwritten Public Offering $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2017USD ($)$ / sharesshares
Subsidiary, Sale of Stock [Line Items]
Number of shares issued and sold (in shares) | shares	1,495,000
Public offering price (in USD per share) | $ / shares	$ 76
Net cash proceeds from shares issued and sold	$ 106.3
Underwriting discounts and commissions	6.8
Other offering expenses	$ 0.5

Stockholder's Equity - Stock Op

Stockholder's Equity - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of Shares
Beginning balance (in shares) | shares	2,876,955
Options exercised (in shares) | shares	(678,825)
Options cancelled (in shares) | shares	(2,866)
Ending balance (in shares) | shares	2,195,264
Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 14.63
Options exercised (in dollars per share) | $ / shares	6.21
Options cancelled (in dollars per share) | $ / shares	16.98
Ending balance (in dollars per share) | $ / shares	$ 17.24

Stockholder's Equity - Restrict

Stockholder's Equity - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted stock and restricted stock units	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of Shares
Unvested beginning balance (in shares) | shares	1,002,944
Granted (in shares) | shares	99,638
Vested (in shares) | shares	(325,023)
Canceled/Forfeited (in shares) | shares	(20,687)
Unvested and expected to vest ending balance (in shares) | shares	756,872
Weighted -Average Grant Date Fair Value
Unvested beginning balance (in dollars per share) | $ / shares	$ 29.44
Granted (in dollars per share) | $ / shares	80.04
Vested (in dollars per share) | $ / shares	24.79
Canceled/Forfeited (in dollars per share) | $ / shares	45.22
Unvested and expected to vest ending balance (in dollars per share) | $ / shares	$ 37.67

Stockholder's Equity - Stock-ba

Stockholder's Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 4,487	$ 4,264	$ 13,092	$ 10,800
Unrecognized compensation cost related to unvested share-based compensation arrangements	30,200		$ 30,200
Unrecognized compensation cost, expected recognition period			2 years 5 months 5 days
Share-based compensation expense, capitalized in inventory			$ 200		$ 400
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	316	83	817	742
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	352	251	913	790
Sales, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,819	$ 3,930	$ 11,362	$ 9,268

Accumulated Other Comprehensi51

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			$ 266,547
Amounts reclassified from accumulated other comprehensive income to earnings:
Ending balance	$ 383,832		383,832
Marketable Investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(38)	$ 206	(105)	$ (163)
Other comprehensive income before reclassifications:
Other comprehensive income before reclassifications	54	(178)	157	401
Income tax effect — (expense) benefit	0	63	0	(145)
Net of tax	54	(115)	157	256
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized losses — marketable investments	0	1	(36)	(3)
Income tax effect — expense	0	(1)	0	1
Net of tax	0	0	(36)	(2)
Net current-year other comprehensive income (loss)	54	(115)	121	254
Ending balance	16	91	16	91
Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,657)	(2,785)	(4,583)	(1,952)
Other comprehensive income before reclassifications:
Other comprehensive income before reclassifications	5,845	(901)	5,771	(1,732)
Income tax effect — (expense) benefit	0	3	0	1
Net of tax	5,845	(898)	5,771	(1,731)
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized losses — marketable investments	0	0	0	0
Income tax effect — expense	0	0	0	0
Net of tax	0	0	0	0
Net current-year other comprehensive income (loss)	5,845	(898)	5,771	(1,731)
Ending balance	1,188	(3,683)	1,188	(3,683)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,695)	(2,579)	(4,688)	(2,115)
Other comprehensive income before reclassifications:
Income tax effect — (expense) benefit	0	66	0	(144)
Net of tax	5,899	(1,013)	5,928	(1,475)
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized losses — marketable investments	0	1	(36)	(3)
Income tax effect — expense	0	(1)	0	1
Net of tax	0	0	(36)	(2)
Net current-year other comprehensive income (loss)	5,899	(1,013)	5,892	(1,477)
Ending balance	$ 1,204	$ (3,592)	$ 1,204	$ (3,592)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Effective tax rate	65.70%	1190.30%	(107.50%)	(2564.10%)
Deferred tax assets, valuation allowance	$ 18.6		$ 18.6

Net Income (Loss) per Share - B

Net Income (Loss) per Share - Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator
Net income (loss)	$ 238	$ 11,906	$ (4,426)	$ 17,210
Denominator
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Basic (in shares)	33,446,841	30,604,384	32,766,135	30,269,463
Potential dilutive shares (in shares)	2,217,431	3,150,999	0	3,098,155
Weighted average shares used to compute net income attributable to common stockholders —Diluted (in shares)	35,664,272	33,755,383	32,766,135	33,367,618
Net (loss) income per share attributable to common stockholders — Basic (in dollars per share)	$ 0.01	$ 0.39	$ (0.14)	$ 0.57
Net (loss) income per share attributable to common stockholders — Diluted (in dollars per share)	$ 0.01	$ 0.35	$ (0.14)	$ 0.52

Net Income (Loss) per Share - A

Net Income (Loss) per Share - Antidilutive Securities (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	21,150	166,950	3,000,000	199,450