Penumbra (PEN) 10-Q 8 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 24, 2018
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	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		34,262,844

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 52,805	$ 50,637
Marketable investments	162,636	163,954
Accounts receivable, net of doubtful accounts of $1,454 and $1,290 at March 31, 2018 and December 31, 2017, respectively	65,107	58,007
Inventories	94,616	94,901
Prepaid expenses and other current assets	12,774	14,735
Total current assets	387,938	382,234
Property and equipment, net	31,995	30,899
Intangible assets, net	28,241	23,778
Goodwill	8,414	8,178
Long-term investments	3,286	3,872
Deferred taxes	28,865	26,690
Other non-current assets	968	1,016
Total assets	489,707	476,667
Current liabilities:
Accounts payable	7,403	6,757
Accrued liabilities	42,850	44,825
Total current liabilities	50,253	51,582
Deferred rent	7,345	6,199
Other non-current liabilities	17,188	18,478
Total liabilities	74,786	76,259
Commitments and contingencies
Stockholders’ equity:
Common stock	34	33
Additional paid-in capital	404,299	396,810
Accumulated other comprehensive income	2,637	1,569
Retained earnings	7,951	1,996
Total stockholders’ equity	414,921	400,408
Total liabilities and stockholders’ equity	$ 489,707	$ 476,667

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,454	$ 1,290

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 102,701	$ 73,213
Cost of revenue	36,144	25,504
Gross profit	66,557	47,709
Operating expenses:
Research and development	8,013	7,034
Sales, general and administrative	54,499	42,721
Total operating expenses	62,512	49,755
Income (loss) from operations	4,045	(2,046)
Interest income, net	749	644
Other expense, net	(290)	(349)
Income (loss) before income taxes and equity in losses of unconsolidated investees	4,504	(1,751)
(Benefit from) provision for income taxes	(1,938)	1,355
Income (loss) before equity in losses of unconsolidated investees	6,442	(3,106)
Equity in losses of unconsolidated investees	(951)	0
Net income (loss)	5,491	(3,106)
Foreign currency translation adjustments, net of tax	1,386	692
Net change in unrealized (losses) gains on available-for-sale securities, net of tax	(318)	70
Total other comprehensive income, net of tax	1,068	762
Comprehensive income (loss)	6,559	(2,344)
Net income (loss)	$ 5,491	$ (3,106)
Net (loss) income per share attributable to common stockholders — Basic (in dollars per share)	$ 0.16	$ (0.10)
Net (loss) income per share attributable to common stockholders — Diluted (in dollars per share)	$ 0.15	$ (0.10)
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Basic (in shares)	33,846,142	31,611,841
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Diluted (in shares)	35,917,051	31,611,841

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 5,491	$ (3,106)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,399	654
Amortization of premium on marketable investments	32	299
Stock-based compensation	4,154	4,012
Loss on non-marketable equity investments	951	0
Inventory write-downs	300	256
Deferred taxes	(2,209)	(1)
Change in fair value of contingent consideration	442	0
Other	357	114
Changes in operating assets and liabilities:
Accounts receivable	(6,109)	(1,880)
Inventories	208	(6,057)
Prepaid expenses and other current and non-current assets	2,986	2,248
Accounts payable	622	889
Accrued expenses and other non-current liabilities	2,084	4,766
Net cash provided by operating activities	10,708	2,194
CASH FLOWS FROM INVESTING ACTIVITIES:
Contributions towards non-marketable investments	(352)	0
Purchase of marketable investments	(42,552)	(44,777)
Proceeds from sales of marketable investments	0	22,975
Proceeds from maturities of marketable investments	43,540	15,020
Purchases of property and equipment	(2,823)	(3,194)
Net cash used in investing activities	(2,187)	(9,976)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Common Stock	0	106,563
Proceeds from exercises of stock options	1,328	1,050
Payment of employee taxes related to vested restricted stock	(3,530)	(2,089)
Payments of Merger Related Costs, Financing Activities	4,323	0
Proceeds from (Payments for) Other Financing Activities	(219)	0
Net cash (used in) provided by financing activities	(6,744)	105,524
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	391	109
Net Increase in Cash and Cash Equivalents and Restricted Cash	2,168	97,851
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH—Beginning of period	50,637	13,236
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH—End of period	52,805	111,087
NONCASH INVESTING AND FINANCING ACTIVITIES:
Common shares issued as consideration in connection with a buyout agreement (Notes 6, 8 and 9)	5,256	0
Purchase of property and equipment funded through accounts payable and accrued liabilities	427	339
Issuance cost not yet paid	0	295
Total cash and cash equivalent and restricted cash - End of period	$ 50,637	$ 13,236

Organization and Description of

Organization and Description of Business	3 Months Ended
	Mar. 31, 2018
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 innovative therapies. The Company designs, develops, manufactures and markets medical devices and has a broad portfolio of products that addresses challenging medical conditions and significant clinical needs.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 , the condensed consolidated statements of operations and comprehensive income (loss) for the three months ended March 31, 2018 and 2017 , and the condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017 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, 2017 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 March 31, 2018 , the results of its operations for the three months ended March 31, 2018 and 2017 , and the cash flows for the three months ended March 31, 2018 and 2017 . The results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 or for any other future annual or interim period. Certain changes in presentation were made in the condensed consolidated financial statements for the three months ended March 31, 2017 to conform to the presentation for the three months ended March 31, 2018 , including the retrospective application of the Accounting Standards Update (“ASU”) 2016-18 as discussed further below . 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, 2017 , included in the Company’s Annual Report on Form 10-K. There have been no changes to the Company’s significant accounting policies during the three months ended March 31, 2018 , 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, 2017 , other than changes to the Company’s revenue policy described below in connection with the adoption of the guidance under the Accounting Standards Codification (“ASC”) 606. 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. Revenue Recognition Revenue is comprised of product revenue net of returns, discounts, administration fees and sales rebates. The Company adopted the guidance under ASC 606 on January 1, 2018 using the modified retrospective method for all contracts not completed as of the date of adoption. Therefore, the comparative prior year information has not been adjusted and continues to be reported under ASC 605 with the impact of the adoption reflected in opening retained earnings. Under ASC 606, the Company recognizes revenue when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Revenue from product sales continue to be recognized either on the date of shipment or the date of receipt by the customer, but is deferred for certain transactions when control has not yet transferred. However, with respect to products that the Company consigns to hospitals, which primarily consist of coils, the Company recognizes revenue at the time hospitals utilize products in a procedure. Deferred revenue represents amounts that the Company has already invoiced its customers and that are ultimately expected to be recognized as revenue, but for which not all revenue recognition criteria have been met. As of March 31, 2018 and December 31, 2017, respectively, the Company's deferred revenue balance was not material. Revenue is recorded at the net sales price, which includes estimates of variable consideration such as return provision, product returns, rebates, discounts, and other adjustments to net revenue. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price. Variable consideration is included in revenue only to the extent that it is probable that a significant reversal of the revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company’s terms and conditions permit product returns and exchanges. The Company bases its estimates for sales returns on actual historical returns over the prior three years and they are recorded as reductions in revenue at the time of sale. Upon recognition, the Company reduces revenue and cost of revenue for the estimated return. Return rates can fluctuate over time, but are sufficiently predictable to allow the Company to estimate expected future product returns. For more information and disclosures on the Company’s revenue, refer to Note “ 13. Revenues .” 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 the first quarter of 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), and its associated amendments. Under the standard, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company applied the five step method outlined in the ASU to all revenue streams and elected to utilize the modified retrospective implementation method. The additional disclosures required by the ASU have been included in Note “ 13. Revenues .” In the first quarter of 2018, the Company adopted ASU No. 2016-18, Statement of Cash Flows: Restricted Cash, a consensus of the Financial Accounting Standards Board (“ FASB”) Emerging Issues Task Force. Under the standard, restricted cash and restricted cash equivalent amounts are presented within cash and cash equivalents when reconciling the total beginning and ending amounts shown on the statement of cash flows. When cash, cash equivalents, restricted cash and restricted cash equivalents are presented in more than one line item on the balance sheet, a reconciliation of the totals in the statement of cash flows to the related captions in the balance sheet is required. The impact of the adoption of ASU No. 2016-18 resulted in a decrease in investing activities and an increase in the ending cash and cash equivalents of $1.7 million in the statement of cash flows for the three months ended March 31, 2017 . In the first quarter of 2018, the Company adopted 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. The guidance was adopted on a prospective basis in the first quarter of 2018 and did not have any impact upon adoption. In the first quarter of 2018, the Company adopted ASU No. 2018-02, Income Statement - Reporting Comprehensive Income. The standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 (the “Tax Reform Act”). The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted for any interim and annual financial statements that have not yet been issued. The Company elected to early adopt this standard on a prospective basis in the first quarter of 2018 and reclassify the stranded tax effects resulting from the Tax Reform Act from accumulated other comprehensive income to retained earnings. There were no additional income tax effects resulting from the Tax Reform Act reclassified from accumulated comprehensive income to retained earnings. The adoption did not have a material impact on the Company’s financial position. In the first quarter of 2018, the Company adopted ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, which included amendments to expand income tax accounting and disclosure guidance pursuant to SEC Staff Accounting Bulletin No. 118 (“SAB 118”) issued by the SEC in December 2017. SAB 118 provides guidance on accounting for the income tax effects of the Tax Reform Act. Refer to Note “ 11. Income Taxes ” for more information and disclosures related to this amended guidance. Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board (“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.

Investments and Fair Value of F

Investments and Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 17,904 $ — $ (11 ) $ 17,893 U.S. treasury 6,402 — (44 ) 6,358 U.S. agency and government sponsored securities 6,214 — (34 ) 6,180 U.S. states and municipalities 13,487 — (29 ) 13,458 Corporate bonds 119,350 23 (626 ) 118,747 Total $ 163,357 $ 23 $ (744 ) $ 162,636 December 31, 2017 Amortized Cost Gross Gross Fair Value Commercial paper $ 19,941 $ — $ (8 ) $ 19,933 U.S. treasury 6,402 — (28 ) 6,374 U.S. agency and government sponsored securities 4,787 — (18 ) 4,769 U.S. states and municipalities 12,510 — (23 ) 12,487 Corporate bonds 120,648 23 (280 ) 120,391 Total $ 164,288 $ 23 $ (357 ) $ 163,954 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 twelve months or more than twelve months as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 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 $ 17,893 $ (11 ) $ — $ — $ 17,893 $ (11 ) U.S. treasury 6,358 (44 ) — — 6,358 (44 ) U.S. agency and government sponsored securities 4,187 (27 ) 1,993 (7 ) 6,180 (34 ) U.S. states and municipalities 10,456 (29 ) — — 10,456 (29 ) Corporate bonds 92,341 (478 ) 9,397 (148 ) 101,738 (626 ) Total $ 131,235 $ (589 ) $ 11,390 $ (155 ) $ 142,625 $ (744 ) December 31, 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 $ 19,933 $ (8 ) $ — $ — $ 19,933 $ (8 ) U.S. treasury 6,374 (28 ) — — 6,374 (28 ) U.S. agency and government sponsored securities 2,778 (9 ) 1,991 (9 ) 4,769 (18 ) U.S. states and municipalities 10,092 (23 ) — — 10,092 (23 ) Corporate bonds 93,284 (188 ) 10,201 (92 ) 103,485 (280 ) Total $ 132,461 $ (256 ) $ 12,192 $ (101 ) $ 144,653 $ (357 ) The contractual maturities of the Company’s marketable investments as of March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, 2018 December 31, 2017 Fair Value Fair Value Due in less than one year $ 141,262 $ 104,272 Due in one to five years 21,374 59,682 Total $ 162,636 $ 163,954 Non-Marketable Equity Investments During the second quarter of 2017, the Company and Sixense Enterprises, Inc. formed a privately-held company, MVI Health Inc. ( “ MVI ” ), with each party holding 50% of the issued and outstanding equity of MVI. Pursuant to agreements between the parties at the time of MVI’s formation, the Company will be obligated to perform certain services or make additional cash contributions to MVI for no additional equity interest. These services include, but are not limited to, information technology, accounting, other administrative services and research and development. The Company’s contributions are presented as a component of “Contributions towards non-marketable investments” in the statement of cash flows. The Company accounted for its investment under the equity method and is not required to consolidate MVI under the voting model. As of March 31, 2018 , 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 March 31, 2018 and December 31, 2017 , the carrying value of the non-marketable equity investment was approximately $3.3 million and $3.9 million , respectively, 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 presented in long-term investments on the condensed consolidated balance sheet. During the three months ended March 31, 2018 , MVI had no revenue and recorded a net loss of $1.9 million . The Company reflected its 50% share of investee losses for the three months ended March 31, 2018 , of $1.0 million , in equity in losses of unconsolidated investees in the condensed consolidated statements of operations and comprehensive income (loss) . The Company held no non-marketable equity investments as of March 31, 2017 . 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 March 31, 2018 Level 1 Level 2 Level 3 Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 11,138 $ — $ 11,138 Money market funds 1,915 — — 1,915 Marketable investments: Commercial paper — 17,893 — 17,893 U.S. treasury 6,358 — — 6,358 U.S. agency and government sponsored securities — 6,180 — 6,180 U.S. states and municipalities — 13,458 — 13,458 Corporate bonds — 118,747 — 118,747 Total $ 8,273 $ 167,416 $ — $ 175,689 Financial Liabilities: Contingent consideration obligations (1) $ — — 14,157 14,157 Total $ — $ — $ 14,157 $ 14,157 As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 9,185 $ — $ 9,185 Money market funds 2,264 — — 2,264 Marketable investments: Commercial paper — 19,933 — 19,933 U.S. treasury 6,374 — — 6,374 U.S. agency and government sponsored securities — 4,769 — 4,769 U.S. states and municipalities — 12,487 — 12,487 Corporate bonds — 120,391 — 120,391 Total $ 8,638 $ 166,765 $ — $ 175,403 Financial Liabilities: Contingent consideration obligations (1) — — 17,392 17,392 Total $ — $ — $ 17,392 $ 17,392 (1) More information on the contingent consideration obligations and the changes in fair value are presented below. The following table summarizes the changes in fair value of the contingent consideration obligation for the three months ended March 31, 2018 (in thousands): Fair Value of Contingent Consideration Crossmed Technology Licensing Agreement Total Balance at December 31, 2017 $ 4,675 $ 12,717 $ 17,392 Payments of contingent consideration liabilities (3,017 ) — (3,017 ) Changes in fair value 442 (793 ) (351 ) Foreign currency remeasurement 133 — 133 Balance at March 31, 2018 $ 2,233 $ 11,924 $ 14,157 As of March 31, 2018 , the Company’s 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 March 31, 2018 , the fair value of the contingent consideration obligations related to the acquisition of Crossmed S.p.A. (“Crossmed”) increased by $0.4 million , which was recorded in sales, general and administrative expense in the condensed consolidated statements of operations and comprehensive income. During the three months ended March 31, 2018 , the fair value of the contingent consideration obligations related to the exclusive technology license agreement decreased by $0.8 million which resulted in a reduction in the related indefinite-lived intangible asset and the liability for the contingent consideration in the condensed consolidated balance sheets. For more information with respect to the nature and fair value of the Company’s contingent consideration obligations, refer to Note “ 5. Business Combination ” and Note “ 6. Intangible Assets ,” respectively. During the three months ended March 31, 2018 and 2017 , 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 March 31, 2018 or December 31, 2017 . During the three months ended March 31, 2018 and 2017 , 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 March 31, 2018 or December 31, 2017 .

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Inventories The following table shows the components of inventories as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Raw materials $ 13,537 $ 13,529 Work in process 8,863 6,073 Finished goods 72,216 75,299 Inventories $ 94,616 $ 94,901 Accrued Liabilities The following table shows the components of accrued liabilities as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Payroll and employee-related cost $ 25,642 $ 22,001 Sales return reserve 3,059 3,035 Preclinical and clinical trial cost 1,879 1,514 Royalty 744 1,115 Product warranty 1,201 1,088 Acquisition-related liabilities 1 1,551 4,752 Other accrued liabilities 8,774 11,320 Total accrued liabilities $ 42,850 $ 44,825 1 Acquisition-related liabilities consists 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 March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Balance at the beginning of the period $ 1,088 $ 1,254 Accruals of warranties issued 232 471 Settlements of warranty claims (119 ) (637 ) Balance at the end of the period $ 1,201 $ 1,088 Other Non-Current Liabilities The following table shows the components of other non-current liabilities as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Deferred tax liabilities $ 3,371 $ 3,299 Licensing-related cost 1 11,924 12,717 Other non-current liabilities 1,893 2,462 Total other non-current liabilities $ 17,188 $ 18,478 1 Amount relates to the liability recorded for probable future milestone payments to be made under the licensing agreement described in Note “ 6. Intangible Assets ,” refer therein for more information.

Business Combination

Business Combination	3 Months Ended
	Mar. 31, 2018
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 was integrated into the Company’s core business. The acquisition of Crossmed did 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, reflecting the measurement period adjustments recorded in the fourth quarter of 2017 (in thousands): Cash, net of working capital and financial debt adjustments $ 11,088 Fair value of contingent consideration for milestone payments 4,343 Contract purchase price $ 15,431 Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra 3,273 Total value of consideration transferred $ 18,704 On 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 is also obligated to pay additional consideration in the form of milestone payments based on Crossmed’s net revenue, and may be required to pay additional consideration based on incr emental net revenue, for the year ended December 31, 2017, and each of the years ending December 31, 2018 and 2019. There is no limit on the milestone payments that can be paid out. During the three months ended March 31, 2018 , the Company made $4.3 million in cash payments to the Sellers, of which $3.0 million related to the achievement of the 2017 milestones and the remainder related to working capital and financial debt adjustments. These payments have been presented as a component of financing activities in the consolidated statement of cash flows due to the nature and timing of the payments. As of March 31, 2018 , the fair value of the current and non-current portion of the related liabilities for the future cash milestone payments recorded on the condensed consolidated balance sheet was $1.0 million and $1.2 million , respectively. 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, 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. During the three months ended March 31, 2018 , the Company recorded $0.4 million of expense in sales, general and administrative expense related to a change in fair value of the contingent consideration as a result of updates to forecasts used in the fair value model based on actual results and changes in estimates. The allocation of the purchase price is preliminary and subject to change within the measurement period (generally one year from the Closing Date), primarily related to the finalization of taxes and working capital. The following table presents the preliminary allocation of the purchase price for Crossmed, reflecting the measurement period adjustments recorded in 2017 (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 1,596 Property and equipment, net 829 Accounts payable (740 ) Accrued liabilities and obligations for short-term debt and credit facilities (1,868 ) 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 7,867 Total purchase price $ 18,704 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 consist 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 amortization of the acquired intangible assets are not deductible for tax purposes. As a result, a $2.5 million deferred tax liability was recorded as of the Closing Date. 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.

Intangible Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2018
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets	6. Intangible Assets Acquired Intangible Assets The following table presents details of the Company’s acquired finite-lived and indefinite-lived intangible assets, as of March 31, 2018 and December 31, 2017 (in thousands, except weighted-average amortization period): As of March 31, 2018 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,348 $ (368 ) $ 6,980 Trade secrets and processes 20.0 years 5,257 (31 ) 5,226 Other 5.0 years 1,895 (284 ) 1,611 Total intangible assets subject to amortization 15.7 years $ 14,500 $ (683 ) $ 13,817 Intangible assets related to licensed technology 14,424 — 14,424 Total intangible assets $ 28,924 $ (683 ) $ 28,241 As of December 31, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,141 $ (238 ) $ 6,903 Other 5.0 years 1,841 (183 ) 1,658 Total intangible assets subject to amortization 13.1 years $ 8,982 $ (421 ) $ 8,561 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,199 $ (421 ) $ 23,778 The customer relationships and other intangible assets subject to amortization relate to the acquisition of Crossmed during the third quarter of 2017. The gross carrying amount and accumulated amortization of these intangible assets are subject to foreign currency translation effects. During the three months ended March 31, 2018 , the Company recorded amortization expense of $0.2 million in sales, general and administrative expense related to these finite-lived intangible assets . Refer to Note “ 5. Business Combination ” for more information. The Company’s $5.3 million trade secrets and processes intangible asset was recognized in connection with a royalty buyout agreement during the first quarter of 2018, which is discussed further in Note “ 8. Commitments and Contingencies ” and Note “ 9. Stockholders’ Equity .” 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 equal to the total payments made and expected to be made under the License Agreement and a corresponding contingent consideration liability for the future milestone payments not yet paid. 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. The fair value of the contingent consideration liability is evaluated at the end of each reporting period. Prior to the commercialization of products utilizing the underlying technology, any changes in fair value of the contingent consideration liability are recorded as an adjustment between the liability balance and the gross carrying amount of the indefinite-lived intangible asset. The contingent consideration is classified as a Level 3 measurement for which fair value is derived 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. During the three months ended March 31, 2018 , the Company recorded a $0.8 million reduction in gross carrying amount of the related indefinite-lived intangible asset related to a change in fair value of the contingent consideration. The fair value of the contingent consideration decreased as a result of changes in the underlying forecasts used to estimate the future milestone payments. As of March 31, 2018 , the balance of the contingent consideration liability related to probable future milestone payments under the Licensing Agreement was $11.9 million and is included in other non-current liabilities on the condensed consolidated balance sheet. As of March 31, 2018 , the gross carrying amount of the indefinite-lived intangible asset was $14.4 million . Refer to Note “ 3. Investments and Fair Value of Financial Instruments ” for more information. During the three months ended March 31, 2018 , the Company noted no events or circumstances that indicate the carrying value of the licensed technology may no longer be recoverable and that an impairment loss may have occurred.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Lease Commitments The Company leases its offices primarily under non–cancelable operating leases that expire at various dates through 2031, subject to its option to renew certain leases for an additional 5 to 15 years . 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 March 31, 2018 and March 31, 2017 was $1.4 million and $1.4 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 other equipment and vehicles primarily under non–cancelable operating 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 March 31, 2018 and December 31, 2017 , 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 shall 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 shall continue until the expiration of the last to expire patent that covers that licensed product or for the period of 15 years following the first commercial sale of such licensed product, whichever is longer. The first commercial sale of covered products occurred in June 2007. 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. The first commercial sale of covered products occurred in April 2014. Unless terminated earlier, the royalty term for each applicable product shall continue for 15 years following the first commercial sale of such patented product, or when the applicable patent covering such product has expired, whichever is sooner. In November 2013, the Company entered into an agreement that required the Company to pay, on a quarterly basis, a 3% royalty on the first $5.0 million in sales and a 1% royalty on sales thereafter of products covered under applicable patents. The agreement was terminated effective January 1, 2018. In April 2015, the Company entered into a royalty agreement that required the Company to pay a 2% royalty on sales of certain products covered by the agreement, on a quarterly basis, in exchange for certain trade secrets and processes which were used to develop such covered products. The Company began the first commercial sale of the covered products in July 2015. In the first quarter of 2018, the Company entered into a buyout of this agreement (the “Buyout Agreement”) in which future royalty payments were canceled in exchange for shares of the Company’s common stock with a fair value of $5.3 million . The Company recorded an intangible asset equal to the $5.3 million buyout amount which will be amortized into cost of sales over the period in which the Company receives future economic benefit . After determining that the pattern of future cash flows associated with this intangible asset could not be reliably estimated with a high level of precision, the Company concluded that the intangible asset will be amortized on a straight‑line basis over its estimated useful life. For more information refer to and Note “ 6. Intangible Assets ” and Note “ 9. Stockholders’ Equity .” Royalty expense included in cost of revenue for the three months ended March 31, 2018 and 2017 , was $0.7 million and $0.8 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. 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 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.

Goodwill Goodwill

Goodwill Goodwill	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	7. Goodwill The following table presents the changes in goodwill during the three months ended March 31, 2018 (in thousands): Total Company Balance as of December 31, 2017 $ 8,178 Foreign currency translation 236 Balance as of March 31, 2018 $ 8,414 Goodwill Impairment Review The Company reviews goodwill for impairment annually during the fourth quarter, on October 31st, or more frequently if events or circumstances indicate that an impairment loss may have occurred. During the three months ended March 31, 2018 , no impairment charges related to goodwill has been identified.

Stockholder's Equity

Stockholder's Equity	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholder's Equity	9. 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 . In the first quarter of 2018, the Company granted and issued 53,256 restricted stock units with a fair value of $5.3 million in connection with the Buyout Agreement, as discussed in Note “ 6. Intangible Assets ” and Note “ 8. Commitments and Contingencies .” The Company recorded the $5.3 million fair value of the shares issued to additional-paid in capital on the condensed consolidated balance sheet upon the issuance of the awards, with the associated expense being amortized into cost of sales over the period in which the Company receives future economic benefit from the buyout. 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 three months ended March 31, 2018 is set forth below: Number of Shares Weighted-Average Exercise Price Balance at December 31, 2017 2,107,104 $ 17.58 Exercised (117,039 ) 11.32 Canceled/Forfeited (633 ) 18.80 Balance at March 31, 2018 1,989,432 17.95 Restricted Stock and Restricted Stock Units Activity of unvested restricted stock and restricted stock units under the Plans during the three months ended March 31, 2018 is set forth below: Number of Shares Weighted -Average Grant Date Fair Value Unvested at December 31, 2017 742,405 $ 38.86 Granted 81,436 100.84 Vested (168,772 ) 48.12 Canceled/Forfeited (1,000 ) 84.65 Unvested at March 31, 2018 654,069 44.11 As of March 31, 2018 , 641,209 restricted stock and restricted stock units are expected to vest. 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 (loss) for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended March 31, 2018 2017 Cost of revenue $ 219 $ 309 Research and development 368 253 Sales, general and administrative 3,567 3,450 Total $ 4,154 $ 4,012 As of March 31, 2018 , total unrecognized compensation cost was $27.6 million related to unvested share-based compensation arrangements which is expected to be recognized over a weighted average period of 2.3 years. The total stock-based compensation cost capitalized in inventory was $0.3 million and $0.2 million as of March 31, 2018 and December 31, 2017 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	10. 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 months ended March 31, 2018 and March 31, 2017 , 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 (loss) (in thousands): Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (235 ) $ 1,804 $ 1,569 $ (105 ) $ (4,583 ) $ (4,688 ) Other comprehensive income before reclassifications: Unrealized (losses) gain— marketable investments (386 ) — (386 ) 101 — 101 Foreign currency translation gains — 1,608 1,608 — 692 692 Income tax effect — benefit (expense) 68 (222 ) (154 ) — — — Net of tax (318 ) 1,386 1,068 101 692 793 Amounts reclassified from accumulated other comprehensive income to earnings: Realized gains — marketable investments — — — (31 ) — (31 ) Income tax effect — expense — — — — — — Net of tax — — — (31 ) — (31 ) Net current-year other comprehensive income (loss) (318 ) 1,386 1,068 70 692 762 Balance at end of the period $ (553 ) $ 3,190 $ 2,637 $ (35 ) $ (3,891 ) $ (3,926 )

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The Company’s income tax expense, deferred tax assets 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 (43.0)% for the three months ended March 31, 2018 , compared to (77.4)% for the three months ended March 31, 2017 . The change in rate was primarily attributable to the partial valuation allowance recorded against its domestic deferred tax assets generated in the three months ended March 31, 2017. On December 22, 2017, the Tax Reform Act was enacted. The Tax Reform Act significantly revised the U.S. corporate income tax regime by, including but not limited to, lowering the U.S. corporate income tax rate to 21% effective January 1, 2018, implementing a territorial tax system, imposing a one-time transition tax on previously untaxed accumulated earnings and profits of foreign subsidiaries, and creating new taxes on foreign sourced earnings. Also on December 22, 2017, the Securities and Exchange Commission issued Staff Accounting Bulletin 118 (“SAB 118”), which provides guidance on accounting for tax effects of the Tax Reform Act. SAB 118 provides a measurement period, that should not extend beyond one year from the Tax Reform Act enactment date, for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Reform Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Reform Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate to be included in the financial statements. In the three months ended March 31, 2018 , the Company recorded a provisional tax charge for the deemed repatriation tax on the undistributed earnings of its foreign subsidiaries. The Company also made sufficient progress on its global intangible low-taxed income tax analysis to reasonably estimate the effects, and therefore reflected provisional amounts in the Company’s financial statements for the three months ended March 31, 2018 . Recording estimates of the tax impact of the deemed repatriation and the global intangible tow taxed income did not have a material effect on the Company’s financial statements. The final impact of the Tax Reform Act may differ from these estimates, due to, among other things, changes in the Company’s interpretations and assumptions, and additional guidance that may be issued. With the adoption of ASU 2016-09, additional deferred tax assets (“DTAs”) of NOL and credits carryforwards were created. With any DTAs, an assessment is necessary to determine if sufficient taxable income will be generated to realize the DTAs and, if not, a substantial valuation allowance to reduce the DTAs may be required. The Company assessed its ability to realize the benefits of its domestic DTAs 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 income, (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 considered its projections of future taxable income in conjunction with relevant provisions of the Tax Reform Act, and concluded that sufficient future taxable income will be generated to realize the benefits of its federal DTAs prior to expiration other than its federal research and development tax credit DTAs. The Company’s federal research and development tax credit DTAs, which have a 20 year carryforward period, are expected to expire prior to utilization based on future projected taxable income. As a result, the Company maintains a valuation allowance against its federal research and development tax credit DTAs as of March 31, 2018 . Consistent with prior periods, the Company maintained a full valuation allowance against its California DTAs as of March 31, 2018 .

Net Income (Loss) per Share

Net Income (Loss) per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net Income (Loss) per Share	12. 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 months ended March 31, 2018 and 2017 is as follows (in thousands, except share and per share amounts): Three Months Ended March 31, 2018 2017 Numerator: Net income (loss) — basic and diluted $ 5,491 $ (3,106 ) Denominator: Weighted average shares used to compute net income (loss): Basic 33,846,142 31,611,841 Effect of dilutive securities from stock-based benefit plans, as calculated using treasury stock method 2,070,909 — Diluted 35,917,051 31,611,841 Net income (loss) per share from: Basic $ 0.16 $ (0.10 ) Diluted $ 0.15 $ (0.10 ) Outstanding stock-based awards of 23.9 thousand and 3.5 million shares for the three months ended March 31, 2018 and 2017 , respectively, were excluded from the computation of diluted net income (loss) per share because their effect would have been anti-dilutive.

Revenues

Revenues	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenues	13. Revenues Adoption of ASC Topic 606, “Revenue from Contracts with Customers” The Company adopted the guidance under ASC 606 on January 1, 2018 using the modified retrospective method for all contracts not completed as of the date of adoption. Therefore, the comparative prior year information has not been adjusted and continues to be reported under ASC 605 with the impact of the adoption reflected in opening retained earnings. As a result of adoption, the cumulative impact to our retained earnings at January 1, 2018 was $0.3 million . The adoption of ASC 606 represents a change in accounting principle that more closely aligns the timing of revenue recognition with the point in time that a performance obligation is satisfied. The Company’s performance obligations are satisfied at a point in time. The implementation of the new standard did not have a material impact on the measurement or recognition of revenue from prior periods, however additional disclosures have been added in accordance with the guidance. As required by ASC 606, the impact of adoption of the new revenue standard on the Company's condensed consolidated statements of operations and comprehensive income and condensed consolidated balance sheets was as follows (in thousands): As of March 31, 2018 Adjusted Balance As Reported Adjustments Without 606 Adoption Consolidated Balance Sheet Data: Assets Accounts receivable, net of doubtful accounts 65,107 (780 ) 64,327 Inventories 94,616 275 94,891 Deferred taxes 28,865 128 28,993 Equity Retained Earnings 7,951 (377 ) 7,574 Three Months Ended March 31, 2018 Adjusted Balance As Reported Adjustments Without 606 Adoption Consolidated Income Statement Data: Revenue 102,701 (122 ) 102,579 Cost of revenue 36,144 (58 ) 36,086 Income (loss) from operations 4,045 (64 ) 3,981 Income (loss) before income taxes and equity in losses of unconsolidated investees 4,504 (64 ) 4,440 (Benefit from) provision for income taxes (1,938 ) 28 (1,910 ) Net income (loss) 5,491 (36 ) 5,455 Revenue Recognition Revenue is recognized in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. All revenue recognized in the income statement is considered to be revenue from contracts with customers. The Company’s revenues disaggregated by geography , based on the destination to which the Company ships its products, for the three months ended March 31, 2018 and 2017 was as follows (in thousands): Three Months Ended March 31, 2018 2017 United States $ 65,801 $ 48,487 Japan 10,682 7,642 Other International 26,218 17,084 Total $ 102,701 $ 73,213 The Company’s revenues disaggregated by product category, for the three months ended March 31, 2018 and 2017 was as follows (in thousands): Three Months Ended March 31, 2018 2017 Neuro $ 71,433 $ 50,249 Peripheral Vascular 31,268 22,964 Total $ 102,701 $ 73,213 Performance Obligations Delivery of Penumbra products - Penumbra’s contracts with customers typically contain a single performance obligation, delivery of Penumbra products. Satisfaction of that performance obligation occurs when control of the promised goods transfers to the customer, which is generally upon shipment for non-consignment sale agreements and upon utilization for consignment sale agreements. Payment terms - Our payment terms vary by the type and location of our customer. The timing between fulfillment of performance obligations and when payment is due is not significant and does not give rise to financing transactions. The Company did not have any contracts with significant financing components as of the period ended March 31, 2018 . Product returns - The Company may allow customers to return products purchased at the Company’s discretion. The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized. The Company currently estimates products return liabilities using its own historic sales information, trends, industry data, and other relevant data points. Warranties - Penumbra offers its standard warranty to all customers and it is not available for sale on a standalone basis. Penumbra’s standard warranty represents its guarantee that its products function as intended, are free from defects, and comply with agreed-upon specifications and quality standards. This assurance does not constitute a service and is not a separate performance obligation. Transaction Price Revenue is recorded at the net sales price, which includes estimates of variable consideration such as return provision, product returns, rebates, discounts, and other adjustments to net revenue. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price. When determining if variable consideration should be constrained, management considers whether there are factors that could result in a significant reversal of revenue and the likelihood of a potential reversal . Variable consideration is included in revenue only to the extent that it is probable that a significant reversal of the revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. These estimates are re-assessed each reporting period as required. When the Company performs shipping and handling activities after control of goods is transferred to the customer, they are considered as fulfillment activities, and costs are accrued for when the related revenue is recognized. Taxes collected from customers relating to product sales and remitted to governmental authorities are excluded from revenues.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated balance sheet as of March 31, 2018 , the condensed consolidated statements of operations and comprehensive income (loss) for the three months ended March 31, 2018 and 2017 , and the condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017 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, 2017 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 March 31, 2018 , the results of its operations for the three months ended March 31, 2018 and 2017 , and the cash flows for the three months ended March 31, 2018 and 2017 . The results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 or for any other future annual or interim period. Certain changes in presentation were made in the condensed consolidated financial statements for the three months ended March 31, 2017 to conform to the presentation for the three months ended March 31, 2018 , including the retrospective application of the Accounting Standards Update (“ASU”) 2016-18 as discussed further below . 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, 2017 , included in the Company’s Annual Report on Form 10-K. There have been no changes to the Company’s significant accounting policies during the three months ended March 31, 2018 , 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, 2017 , other than changes to the Company’s revenue policy described below in connection with the adoption of the guidance under the Accounting Standards Codification (“ASC”) 606. 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.
Revenue Recognition	Revenue Recognition Revenue is comprised of product revenue net of returns, discounts, administration fees and sales rebates. The Company adopted the guidance under ASC 606 on January 1, 2018 using the modified retrospective method for all contracts not completed as of the date of adoption. Therefore, the comparative prior year information has not been adjusted and continues to be reported under ASC 605 with the impact of the adoption reflected in opening retained earnings. Under ASC 606, the Company recognizes revenue when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Revenue from product sales continue to be recognized either on the date of shipment or the date of receipt by the customer, but is deferred for certain transactions when control has not yet transferred. However, with respect to products that the Company consigns to hospitals, which primarily consist of coils, the Company recognizes revenue at the time hospitals utilize products in a procedure. Deferred revenue represents amounts that the Company has already invoiced its customers and that are ultimately expected to be recognized as revenue, but for which not all revenue recognition criteria have been met. As of March 31, 2018 and December 31, 2017, respectively, the Company's deferred revenue balance was not material. Revenue is recorded at the net sales price, which includes estimates of variable consideration such as return provision, product returns, rebates, discounts, and other adjustments to net revenue. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price. Variable consideration is included in revenue only to the extent that it is probable that a significant reversal of the revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company’s terms and conditions permit product returns and exchanges. The Company bases its estimates for sales returns on actual historical returns over the prior three years and they are recorded as reductions in revenue at the time of sale. Upon recognition, the Company reduces revenue and cost of revenue for the estimated return. Return rates can fluctuate over time, but are sufficiently predictable to allow the Company to estimate expected future product returns. For more information and disclosures on the Company’s revenue, refer to Note “ 13. Revenues .”
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 the first quarter of 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), and its associated amendments. Under the standard, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company applied the five step method outlined in the ASU to all revenue streams and elected to utilize the modified retrospective implementation method. The additional disclosures required by the ASU have been included in Note “ 13. Revenues .” In the first quarter of 2018, the Company adopted ASU No. 2016-18, Statement of Cash Flows: Restricted Cash, a consensus of the Financial Accounting Standards Board (“ FASB”) Emerging Issues Task Force. Under the standard, restricted cash and restricted cash equivalent amounts are presented within cash and cash equivalents when reconciling the total beginning and ending amounts shown on the statement of cash flows. When cash, cash equivalents, restricted cash and restricted cash equivalents are presented in more than one line item on the balance sheet, a reconciliation of the totals in the statement of cash flows to the related captions in the balance sheet is required. The impact of the adoption of ASU No. 2016-18 resulted in a decrease in investing activities and an increase in the ending cash and cash equivalents of $1.7 million in the statement of cash flows for the three months ended March 31, 2017 . In the first quarter of 2018, the Company adopted 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. The guidance was adopted on a prospective basis in the first quarter of 2018 and did not have any impact upon adoption. In the first quarter of 2018, the Company adopted ASU No. 2018-02, Income Statement - Reporting Comprehensive Income. The standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 (the “Tax Reform Act”). The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted for any interim and annual financial statements that have not yet been issued. The Company elected to early adopt this standard on a prospective basis in the first quarter of 2018 and reclassify the stranded tax effects resulting from the Tax Reform Act from accumulated other comprehensive income to retained earnings. There were no additional income tax effects resulting from the Tax Reform Act reclassified from accumulated comprehensive income to retained earnings. The adoption did not have a material impact on the Company’s financial position. In the first quarter of 2018, the Company adopted ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, which included amendments to expand income tax accounting and disclosure guidance pursuant to SEC Staff Accounting Bulletin No. 118 (“SAB 118”) issued by the SEC in December 2017. SAB 118 provides guidance on accounting for the income tax effects of the Tax Reform Act. Refer to Note “ 11. Income Taxes ” for more information and disclosures related to this amended guidance. Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board (“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.

Investments and Fair Value of20

Investments and Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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 March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 17,904 $ — $ (11 ) $ 17,893 U.S. treasury 6,402 — (44 ) 6,358 U.S. agency and government sponsored securities 6,214 — (34 ) 6,180 U.S. states and municipalities 13,487 — (29 ) 13,458 Corporate bonds 119,350 23 (626 ) 118,747 Total $ 163,357 $ 23 $ (744 ) $ 162,636 December 31, 2017 Amortized Cost Gross Gross Fair Value Commercial paper $ 19,941 $ — $ (8 ) $ 19,933 U.S. treasury 6,402 — (28 ) 6,374 U.S. agency and government sponsored securities 4,787 — (18 ) 4,769 U.S. states and municipalities 12,510 — (23 ) 12,487 Corporate bonds 120,648 23 (280 ) 120,391 Total $ 164,288 $ 23 $ (357 ) $ 163,954
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 twelve months or more than twelve months as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 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 $ 17,893 $ (11 ) $ — $ — $ 17,893 $ (11 ) U.S. treasury 6,358 (44 ) — — 6,358 (44 ) U.S. agency and government sponsored securities 4,187 (27 ) 1,993 (7 ) 6,180 (34 ) U.S. states and municipalities 10,456 (29 ) — — 10,456 (29 ) Corporate bonds 92,341 (478 ) 9,397 (148 ) 101,738 (626 ) Total $ 131,235 $ (589 ) $ 11,390 $ (155 ) $ 142,625 $ (744 ) December 31, 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 $ 19,933 $ (8 ) $ — $ — $ 19,933 $ (8 ) U.S. treasury 6,374 (28 ) — — 6,374 (28 ) U.S. agency and government sponsored securities 2,778 (9 ) 1,991 (9 ) 4,769 (18 ) U.S. states and municipalities 10,092 (23 ) — — 10,092 (23 ) Corporate bonds 93,284 (188 ) 10,201 (92 ) 103,485 (280 ) Total $ 132,461 $ (256 ) $ 12,192 $ (101 ) $ 144,653 $ (357 )
Schedule of Contractual Maturities of Marketable Investments		The contractual maturities of the Company’s marketable investments as of March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, 2018 December 31, 2017 Fair Value Fair Value Due in less than one year $ 141,262 $ 104,272 Due in one to five years 21,374 59,682 Total $ 162,636 $ 163,954
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 March 31, 2018 Level 1 Level 2 Level 3 Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 11,138 $ — $ 11,138 Money market funds 1,915 — — 1,915 Marketable investments: Commercial paper — 17,893 — 17,893 U.S. treasury 6,358 — — 6,358 U.S. agency and government sponsored securities — 6,180 — 6,180 U.S. states and municipalities — 13,458 — 13,458 Corporate bonds — 118,747 — 118,747 Total $ 8,273 $ 167,416 $ — $ 175,689 Financial Liabilities: Contingent consideration obligations (1) $ — — 14,157 14,157 Total $ — $ — $ 14,157 $ 14,157 As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Financial Assets Cash equivalents: Commercial paper $ — $ 9,185 $ — $ 9,185 Money market funds 2,264 — — 2,264 Marketable investments: Commercial paper — 19,933 — 19,933 U.S. treasury 6,374 — — 6,374 U.S. agency and government sponsored securities — 4,769 — 4,769 U.S. states and municipalities — 12,487 — 12,487 Corporate bonds — 120,391 — 120,391 Total $ 8,638 $ 166,765 $ — $ 175,403 Financial Liabilities: Contingent consideration obligations (1) — — 17,392 17,392 Total $ — $ — $ 17,392 $ 17,392 (1) More information on the contingent consideration obligations and the changes in fair value are presented below.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	The following table summarizes the changes in fair value of the contingent consideration obligation for the three months ended March 31, 2018 (in thousands): Fair Value of Contingent Consideration Crossmed Technology Licensing Agreement Total Balance at December 31, 2017 $ 4,675 $ 12,717 $ 17,392 Payments of contingent consideration liabilities (3,017 ) — (3,017 ) Changes in fair value 442 (793 ) (351 ) Foreign currency remeasurement 133 — 133 Balance at March 31, 2018 $ 2,233 $ 11,924 $ 14,157

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventories	The following table shows the components of inventories as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Raw materials $ 13,537 $ 13,529 Work in process 8,863 6,073 Finished goods 72,216 75,299 Inventories $ 94,616 $ 94,901
Schedule of Accrued Liabilities	The following table shows the components of accrued liabilities as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Payroll and employee-related cost $ 25,642 $ 22,001 Sales return reserve 3,059 3,035 Preclinical and clinical trial cost 1,879 1,514 Royalty 744 1,115 Product warranty 1,201 1,088 Acquisition-related liabilities 1 1,551 4,752 Other accrued liabilities 8,774 11,320 Total accrued liabilities $ 42,850 $ 44,825
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 March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Balance at the beginning of the period $ 1,088 $ 1,254 Accruals of warranties issued 232 471 Settlements of warranty claims (119 ) (637 ) Balance at the end of the period $ 1,201 $ 1,088
Schedule of Other Non-Current Liabilities	The following table shows the components of other non-current liabilities as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Deferred tax liabilities $ 3,371 $ 3,299 Licensing-related cost 1 11,924 12,717 Other non-current liabilities 1,893 2,462 Total other non-current liabilities $ 17,188 $ 18,478 1 Amount relates to the liability recorded for probable future milestone payments to be made under the licensing agreement described in Note “ 6. Intangible Assets ,” refer therein for more information.

Business Combination (Tables)

Business Combination (Tables)	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Schedule of Business Acquisition Consideration Transferred	The following table summarizes the Closing Date fair value of the consideration transferred, reflecting the measurement period adjustments recorded in the fourth quarter of 2017 (in thousands): Cash, net of working capital and financial debt adjustments $ 11,088 Fair value of contingent consideration for milestone payments 4,343 Contract purchase price $ 15,431 Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra 3,273 Total value of consideration transferred $ 18,704
Schedule of Purchase Price Allocation	The following table presents the preliminary allocation of the purchase price for Crossmed, reflecting the measurement period adjustments recorded in 2017 (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 1,596 Property and equipment, net 829 Accounts payable (740 ) Accrued liabilities and obligations for short-term debt and credit facilities (1,868 ) 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 7,867 Total purchase price $ 18,704

Intangible Assets (Tables)

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Schedule of finite-lived intangible assets	The following table presents details of the Company’s acquired finite-lived and indefinite-lived intangible assets, as of March 31, 2018 and December 31, 2017 (in thousands, except weighted-average amortization period): As of March 31, 2018 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,348 $ (368 ) $ 6,980 Trade secrets and processes 20.0 years 5,257 (31 ) 5,226 Other 5.0 years 1,895 (284 ) 1,611 Total intangible assets subject to amortization 15.7 years $ 14,500 $ (683 ) $ 13,817 Intangible assets related to licensed technology 14,424 — 14,424 Total intangible assets $ 28,924 $ (683 ) $ 28,241 As of December 31, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,141 $ (238 ) $ 6,903 Other 5.0 years 1,841 (183 ) 1,658 Total intangible assets subject to amortization 13.1 years $ 8,982 $ (421 ) $ 8,561 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,199 $ (421 ) $ 23,778
Schedule of indefinite-lived intangible assets	The following table presents details of the Company’s acquired finite-lived and indefinite-lived intangible assets, as of March 31, 2018 and December 31, 2017 (in thousands, except weighted-average amortization period): As of March 31, 2018 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,348 $ (368 ) $ 6,980 Trade secrets and processes 20.0 years 5,257 (31 ) 5,226 Other 5.0 years 1,895 (284 ) 1,611 Total intangible assets subject to amortization 15.7 years $ 14,500 $ (683 ) $ 13,817 Intangible assets related to licensed technology 14,424 — 14,424 Total intangible assets $ 28,924 $ (683 ) $ 28,241 As of December 31, 2017 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Customer relationships 15.0 years $ 7,141 $ (238 ) $ 6,903 Other 5.0 years 1,841 (183 ) 1,658 Total intangible assets subject to amortization 13.1 years $ 8,982 $ (421 ) $ 8,561 Intangible assets related to licensed technology 15,217 — 15,217 Total intangible assets $ 24,199 $ (421 ) $ 23,778

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill	The following table presents the changes in goodwill during the three months ended March 31, 2018 (in thousands): Total Company Balance as of December 31, 2017 $ 8,178 Foreign currency translation 236 Balance as of March 31, 2018 $ 8,414

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	3 Months Ended
	Mar. 31, 2018
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 three months ended March 31, 2018 is set forth below: Number of Shares Weighted-Average Exercise Price Balance at December 31, 2017 2,107,104 $ 17.58 Exercised (117,039 ) 11.32 Canceled/Forfeited (633 ) 18.80 Balance at March 31, 2018 1,989,432 17.95
Summary of Unvested Restricted Stock and Restricted Stock Unit Activity	Activity of unvested restricted stock and restricted stock units under the Plans during the three months ended March 31, 2018 is set forth below: Number of Shares Weighted -Average Grant Date Fair Value Unvested at December 31, 2017 742,405 $ 38.86 Granted 81,436 100.84 Vested (168,772 ) 48.12 Canceled/Forfeited (1,000 ) 84.65 Unvested at March 31, 2018 654,069 44.11
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 (loss) for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended March 31, 2018 2017 Cost of revenue $ 219 $ 309 Research and development 368 253 Sales, general and administrative 3,567 3,450 Total $ 4,154 $ 4,012

Accumulated Other Comprehensi26

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes the changes in the accumulated balances during the three months ended March 31, 2018 and March 31, 2017 , 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 (loss) (in thousands): Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Marketable Currency Translation Total Marketable Currency Translation Total Balance at beginning of the period $ (235 ) $ 1,804 $ 1,569 $ (105 ) $ (4,583 ) $ (4,688 ) Other comprehensive income before reclassifications: Unrealized (losses) gain— marketable investments (386 ) — (386 ) 101 — 101 Foreign currency translation gains — 1,608 1,608 — 692 692 Income tax effect — benefit (expense) 68 (222 ) (154 ) — — — Net of tax (318 ) 1,386 1,068 101 692 793 Amounts reclassified from accumulated other comprehensive income to earnings: Realized gains — marketable investments — — — (31 ) — (31 ) Income tax effect — expense — — — — — — Net of tax — — — (31 ) — (31 ) Net current-year other comprehensive income (loss) (318 ) 1,386 1,068 70 692 762 Balance at end of the period $ (553 ) $ 3,190 $ 2,637 $ (35 ) $ (3,891 ) $ (3,926 )

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	3 Months Ended
	Mar. 31, 2018
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 months ended March 31, 2018 and 2017 is as follows (in thousands, except share and per share amounts): Three Months Ended March 31, 2018 2017 Numerator: Net income (loss) — basic and diluted $ 5,491 $ (3,106 ) Denominator: Weighted average shares used to compute net income (loss): Basic 33,846,142 31,611,841 Effect of dilutive securities from stock-based benefit plans, as calculated using treasury stock method 2,070,909 — Diluted 35,917,051 31,611,841 Net income (loss) per share from: Basic $ 0.16 $ (0.10 ) Diluted $ 0.15 $ (0.10 )

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	As required by ASC 606, the impact of adoption of the new revenue standard on the Company's condensed consolidated statements of operations and comprehensive income and condensed consolidated balance sheets was as follows (in thousands): As of March 31, 2018 Adjusted Balance As Reported Adjustments Without 606 Adoption Consolidated Balance Sheet Data: Assets Accounts receivable, net of doubtful accounts 65,107 (780 ) 64,327 Inventories 94,616 275 94,891 Deferred taxes 28,865 128 28,993 Equity Retained Earnings 7,951 (377 ) 7,574 Three Months Ended March 31, 2018 Adjusted Balance As Reported Adjustments Without 606 Adoption Consolidated Income Statement Data: Revenue 102,701 (122 ) 102,579 Cost of revenue 36,144 (58 ) 36,086 Income (loss) from operations 4,045 (64 ) 3,981 Income (loss) before income taxes and equity in losses of unconsolidated investees 4,504 (64 ) 4,440 (Benefit from) provision for income taxes (1,938 ) 28 (1,910 ) Net income (loss) 5,491 (36 ) 5,455
Disaggregation of Revenue	The Company’s revenues disaggregated by geography , based on the destination to which the Company ships its products, for the three months ended March 31, 2018 and 2017 was as follows (in thousands): Three Months Ended March 31, 2018 2017 United States $ 65,801 $ 48,487 Japan 10,682 7,642 Other International 26,218 17,084 Total $ 102,701 $ 73,213 The Company’s revenues disaggregated by product category, for the three months ended March 31, 2018 and 2017 was as follows (in thousands): Three Months Ended March 31, 2018 2017 Neuro $ 71,433 $ 50,249 Peripheral Vascular 31,268 22,964 Total $ 102,701 $ 73,213

Summary of Significant Accoun29

Summary of Significant Accounting Policies - Additional Disclosures (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segmentactivity	Dec. 31, 2017USD ($)	Mar. 31, 2017USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of business activities | activity	1
Number of Operating Segments | segment	1
Cash and cash equivalents	$ 52,805	$ 50,637	$ 109,383
Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 1,700

Investments and Fair Value of30

Investments and Fair Value of Financial Instruments - Gains and Losses of Marketable Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 163,357	$ 164,288
Gross Unrealized Gains	23	23
Gross Unrealized Losses	(744)	(357)
Fair Value	162,636	163,954
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,904	19,941
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(11)	(8)
Fair Value	17,893	19,933
U.S. treasury
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,402	6,402
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(44)	(28)
Fair Value	6,358	6,374
U.S. agency and government sponsored securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,214	4,787
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(34)	(18)
Fair Value	6,180	4,769
U.S. states and municipalities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,487	12,510
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(29)	(23)
Fair Value	13,458	12,487
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	119,350	120,648
Gross Unrealized Gains	23	23
Gross Unrealized Losses	(626)	(280)
Fair Value	$ 118,747	$ 120,391

Investments and Fair Value of31

Investments and Fair Value of Financial Instruments - Marketable Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	$ 131,235	$ 132,461
Less than 12 months: Gross Unrealized Losses	(589)	(256)
12 Months of more: Fair Value	11,390	12,192
12 months or more: Gross Unrealized Losses	(155)	(101)
Total: Fair Value	142,625	144,653
Total: Gross Unrealized Losses	(744)	(357)
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	17,893	19,933
Less than 12 months: Gross Unrealized Losses	(11)	(8)
12 Months of more: Fair Value	0	0
12 months or more: Gross Unrealized Losses	0	0
Total: Fair Value	17,893	19,933
Total: Gross Unrealized Losses	(11)	(8)
U.S. treasury
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	6,358	6,374
Less than 12 months: Gross Unrealized Losses	(44)	(28)
12 Months of more: Fair Value	0	0
12 months or more: Gross Unrealized Losses	0	0
Total: Fair Value	6,358	6,374
Total: Gross Unrealized Losses	(44)	(28)
U.S. agency and government sponsored securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	4,187	2,778
Less than 12 months: Gross Unrealized Losses	(27)	(9)
12 Months of more: Fair Value	1,993	1,991
12 months or more: Gross Unrealized Losses	(7)	(9)
Total: Fair Value	6,180	4,769
Total: Gross Unrealized Losses	(34)	(18)
U.S. states and municipalities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	10,456	10,092
Less than 12 months: Gross Unrealized Losses	(29)	(23)
12 Months of more: Fair Value	0	0
12 months or more: Gross Unrealized Losses	0	0
Total: Fair Value	10,456	10,092
Total: Gross Unrealized Losses	(29)	(23)
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	92,341	93,284
Less than 12 months: Gross Unrealized Losses	(478)	(188)
12 Months of more: Fair Value	9,397	10,201
12 months or more: Gross Unrealized Losses	(148)	(92)
Total: Fair Value	101,738	103,485
Total: Gross Unrealized Losses	$ (626)	$ (280)

Investments and Fair Value of32

Investments and Fair Value of Financial Instruments - Contractual Maturities of Marketable Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Due in less than one year	$ 141,262	$ 104,272
Due in one to five years	21,374	59,682
Total	$ 162,636	$ 163,954

Investments and Fair Value of33

Investments and Fair Value of Financial Instruments - Non-Marketable Equity Investments (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Carrying value of investment			$ 0
Revenue	$ 102,701,000	$ 73,213,000
Net loss from equity investments	$ 951,000	$ 0
MVI
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	50.00%
Carrying value of investment	$ 3,300,000		$ 3,900,000
Revenue	0
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	1,900,000
Parent Company [Member] | Other Expenses, net | MVI
Schedule of Equity Method Investments [Line Items]
Net loss from equity investments	$ (1,000,000)

Investments and Fair Value of34

Investments and Fair Value of Financial Instruments - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Licensing-related cost, Noncurrent	$ 11,924	$ 12,717
Recurring
Financial Assets
Total	175,689	175,403
Financial Liabilities Fair Value Disclosure	14,157	17,392
Recurring | Commercial paper
Financial Assets
Marketable investments	17,893	19,933
Recurring | U.S. treasury
Financial Assets
Marketable investments	6,358	6,374
Recurring | U.S. agency and government sponsored securities
Financial Assets
Marketable investments	6,180	4,769
Recurring | U.S. states and municipalities
Financial Assets
Marketable investments	13,458	12,487
Recurring | Corporate bonds
Financial Assets
Marketable investments	118,747	120,391
Recurring | Commercial paper
Financial Assets
Cash equivalents	11,138	9,185
Recurring | Money market funds
Financial Assets
Cash equivalents	1,915	2,264
Recurring | Level 1
Financial Assets
Total	8,273	8,638
Financial Liabilities Fair Value Disclosure	0	0
Recurring | Level 1 | Commercial paper
Financial Assets
Marketable investments	0	0
Recurring | Level 1 | U.S. treasury
Financial Assets
Marketable investments	6,358	6,374
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 | Commercial paper
Financial Assets
Cash equivalents	0	0
Recurring | Level 1 | Money market funds
Financial Assets
Cash equivalents	1,915	2,264
Recurring | Level 2
Financial Assets
Total	167,416	166,765
Financial Liabilities Fair Value Disclosure	0	0
Recurring | Level 2 | Commercial paper
Financial Assets
Marketable investments	17,893	19,933
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	6,180	4,769
Recurring | Level 2 | U.S. states and municipalities
Financial Assets
Marketable investments	13,458	12,487
Recurring | Level 2 | Corporate bonds
Financial Assets
Marketable investments	118,747	120,391
Recurring | Level 2 | Commercial paper
Financial Assets
Cash equivalents	11,138	9,185
Recurring | Level 2 | Money market funds
Financial Assets
Cash equivalents	0	0
Recurring | Fair Value, Inputs, Level 3 [Member]
Financial Assets
Total	0	0
Financial Liabilities Fair Value Disclosure	14,157	17,392
Recurring | Fair Value, Inputs, Level 3 [Member] | Commercial paper
Financial Assets
Marketable investments	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | U.S. treasury
Financial Assets
Marketable investments	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | U.S. agency and government sponsored securities
Financial Assets
Marketable investments	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | U.S. states and municipalities
Financial Assets
Marketable investments	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | Corporate bonds
Financial Assets
Marketable investments	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | Commercial paper
Financial Assets
Cash equivalents	0	0
Recurring | Fair Value, Inputs, Level 3 [Member] | Money market funds
Financial Assets
Cash equivalents	0	0
Contingent Consideration Liability | Recurring
Financial Assets
Financial Liabilities Fair Value Disclosure	14,157	17,392
Contingent Consideration Liability | Recurring | Level 1
Financial Assets
Financial Liabilities Fair Value Disclosure	0	0
Contingent Consideration Liability | Recurring | Level 2
Financial Assets
Financial Liabilities Fair Value Disclosure	0	0
Contingent Consideration Liability | Recurring | Fair Value, Inputs, Level 3 [Member]
Financial Assets
Financial Liabilities Fair Value Disclosure	$ 14,157	$ 17,392

Investments and Fair Value of35

Investments and Fair Value of Financial Instruments - Contingent Consideration (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
December 31, 2017	$ 17,392
Payments of contingent consideration liabilities	(3,017)
Changes in fair value	(351)
Foreign currency remeasurement	133
March 31, 2018	14,157
Crossmed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
December 31, 2017	4,675
Payments of contingent consideration liabilities	(3,017)
Changes in fair value	442
Foreign currency remeasurement	133
March 31, 2018	2,233
Technology Licensing Agreement
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
December 31, 2017	12,717
Payments of contingent consideration liabilities	0
Changes in fair value	(793)
Foreign currency remeasurement	0
March 31, 2018	$ 11,924

Balance Sheet Components - Inve

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 13,537	$ 13,529
Work in process	8,863	6,073
Finished goods	72,216	75,299
Inventories	$ 94,616	$ 94,901

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Payroll and employee-related cost	$ 25,642	$ 22,001
Sales return reserve	3,059	3,035
Preclinical and clinical trial cost	1,879	1,514
Royalty	744	1,115
Product warranty	1,201	1,088
Acquisition-related liabilities1	1,551	4,752
Other accrued liabilities	8,774	11,320
Total accrued liabilities	$ 42,850	$ 44,825

Balance Sheet Components - Prod

Balance Sheet Components - Product Warranty (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Product Warranty, Increase (Decrease) [Roll Forward]
Balance at the beginning of the period	$ 1,088	$ 1,254
Accruals of warranties issued	232	471
Settlements of warranty claims	(119)	(637)
Balance at the end of the period	$ 1,201	$ 1,088

Balance Sheet Components - Othe

Balance Sheet Components - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred tax liabilities	$ 3,371	$ 3,299
Licensing-related cost, Noncurrent	11,924	12,717
Other Accrued Liabilities, Noncurrent	1,893	2,462
Total other non-current liabilities	$ 17,188	$ 18,478

Business Combination - Narrati

Business Combination - Narrative (Details) $ in Thousands, € in Millions	Jul. 03, 2017EUR (€)	Jul. 03, 2017USD ($)	Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)
Business Acquisition [Line Items]
Number of Operating Segments | segment			1
Payments of Merger Related Costs, Financing Activities			$ 4,323	$ 0
Revenue			102,701	73,213
Net income (loss)			5,491	$ (3,106)
Crossmed
Business Acquisition [Line Items]
Payments to acquire business	€ 8.2	$ 9,400
Contingent Consideration Arrangements, Range of Outcomes, Maximum Unlimited				0
Payments of Merger Related Costs, Financing Activities			4,300
Contingent consideration for milestone payments		4,343
Deferred Tax Liabilities, Net		$ 2,472	2,500
Current Liabilities | Crossmed
Business Acquisition [Line Items]
Contingent consideration for milestone payments			1,000
2017 Milestone Achievement Payment | Crossmed
Business Acquisition [Line Items]
Payments of Merger Related Costs, Financing Activities			$ 3,000

Business Combination - Consider

Business Combination - Consideration Transferred (Details) - USD ($) $ in Thousands	Jul. 03, 2017	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Change in fair value of contingent consideration		$ 442	$ 0
Crossmed
Business Acquisition [Line Items]
Purchase Consideration To Acquire Businesses Net Of Working Capital Adjustments Excluding Contingent Consideration	$ 11,088
Fair value of contingent consideration for milestone payments	4,343
Contract purchase price	15,431
Consideration for settlement of pre-existing receivable due from Crossmed to Penumbra	3,273
Total value of consideration transferred	$ 18,704
Noncurrent Liabilities | Crossmed
Business Acquisition [Line Items]
Fair value of contingent consideration for milestone payments		1,200
Current Liabilities | Crossmed
Business Acquisition [Line Items]
Fair value of contingent consideration for milestone payments		1,000
Sales, general and administrative | Crossmed
Business Acquisition [Line Items]
Change in fair value of contingent consideration		$ 400

Business Combination - Purchase

Business Combination - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Jul. 03, 2017	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Estimated Useful Life of Finite-Lived Intangible Assets		15 years 8 months 12 days	13 years 1 month 6 days
Goodwill		$ 8,414	$ 8,178
Crossmed
Business Acquisition [Line Items]
Accounts receivable	$ 4,406
Inventories	1,343
Other current and non-current assets	1,596
Property and equipment, net	829
Accounts payable	(740)
Accrued liabilities and obligations for short-term debt and credit facilities	(1,868)
Deferred Tax Liabilities, Net	(2,472)	$ (2,500)
Other non-current liabilities	(797)
Goodwill	7,867
Total purchase price	18,704
Customer relationships
Business Acquisition [Line Items]
Estimated Useful Life of Finite-Lived Intangible Assets		15 years	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	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

Intangible Assets - Intangible

Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	15 years 8 months 12 days		13 years 1 month 6 days
Finite lived intangible assets: gross carrying amount	$ 14,500		$ 8,982
Accumulated amortization	(683)		(421)
Finite lived intangible assets: net	13,817		8,561
Indefinite-lived intangible assets	14,424		15,217
Total intangible assets, gross	28,924		24,199
Total intangible assets, net	28,241		23,778
Amortization of Intangible Assets	200
Payments to acquire intangible assets		$ 2,500
Changes in fair value	(351)
Licensing-related cost, Noncurrent	$ 11,924		$ 12,717
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	15 years		15 years
Finite lived intangible assets: gross carrying amount	$ 7,348		$ 7,141
Accumulated amortization	(368)		(238)
Finite lived intangible assets: net	$ 6,980		$ 6,903
Trade secrets and processes
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	20 years
Finite lived intangible assets: gross carrying amount	$ 5,257
Accumulated amortization	(31)
Finite lived intangible assets: net	$ 5,226
Other
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	5 years		5 years
Finite lived intangible assets: gross carrying amount	$ 1,895		$ 1,841
Accumulated amortization	(284)		(183)
Finite lived intangible assets: net	$ 1,611		$ 1,658

Commitments and Contingencies -

Commitments and Contingencies - Lease and Purchase Commitments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Leases [Line Items]
Rent expense	$ 1.4	$ 1.4
Headquarters, Additional Lease [Member] | Minimum [Member]
Operating Leases [Line Items]
Lessor, Operating Lease, Renewal Term	5 years
Headquarters, Additional Lease [Member] | Maximum [Member]
Operating Leases [Line Items]
Lessor, Operating Lease, Renewal Term	15 years

Commitments and Contingencies45

Commitments and Contingencies - Royalty Obligations (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Other Commitments [Line Items]
Common shares issued as consideration in connection with a buyout agreement (Notes 6, 8 and 9)	$ 5,256,000	$ 0
Finite lived intangible assets: gross carrying amount	14,500,000		$ 8,982,000
Cost of Sales
Other Commitments [Line Items]
Royalty expense	700,000	$ 800,000
Royalty Agreement, March 2005
Other Commitments [Line Items]
Minimum annual royalty payments	$ 100,000		$ 100,000
Term of agreement	15 years
Royalty Agreement, April 2012
Other Commitments [Line Items]
Term of agreement	15 years
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%
Common shares issued as consideration in connection with a buyout agreement (Notes 6, 8 and 9)	$ 5,300,000
Trade secrets and processes
Other Commitments [Line Items]
Finite lived intangible assets: gross carrying amount	$ 5,257,000

Goodwill (Details)

Goodwill (Details)	3 Months Ended
	Mar. 31, 2018USD ($)
Goodwill [Roll Forward]
Goodwill	$ 8,178,000
Foreign currency translation	236,000
Goodwill	8,414,000
Impairment loss	$ 0

Stockholder's Equity - Common S

Stockholder's Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Common shares issued as consideration in connection with a buyout agreement (Notes 6, 8 and 9)		$ 5,256	$ 0
Underwritten Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued and sold (in shares)	1,495,000
Public offering price (in USD per share)	$ 76		$ 76
Net cash proceeds from shares issued and sold	$ 106,300
Underwriting discounts and commissions	6,800
Other offering expenses	$ 500
Restricted Stock Units (RSUs)
Subsidiary, Sale of Stock [Line Items]
Granted (in shares)		53,256
Royalty Agreement, April 2015
Subsidiary, Sale of Stock [Line Items]
Common shares issued as consideration in connection with a buyout agreement (Notes 6, 8 and 9)		$ 5,300

Stockholder's Equity - Stock Op

Stockholder's Equity - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Shares
Beginning balance (in shares) | shares	2,107,104
Options exercised (in shares) | shares	(117,039)
Options cancelled (in shares) | shares	(633)
Ending balance (in shares) | shares	1,989,432
Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 17.58
Options exercised (in dollars per share) | $ / shares	11.32
Options cancelled (in dollars per share) | $ / shares	18.80
Ending balance (in dollars per share) | $ / shares	$ 17.95

Stockholder's Equity - Restrict

Stockholder's Equity - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted stock and restricted stock units	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Shares
Unvested beginning balance (in shares)	742,405
Granted (in shares)	81,436
Vested (in shares)	(168,772)
Canceled/Forfeited (in shares)	(1,000)
Unvested and expected to vest ending balance (in shares)	654,069
Weighted -Average Grant Date Fair Value
Unvested beginning balance (in dollars per share) | $ / shares	$ 38.86
Granted (in dollars per share) | $ / shares	100.84
Vested (in dollars per share) | $ / shares	48.12
Canceled/Forfeited (in dollars per share) | $ / shares	84.65
Unvested and expected to vest ending balance (in dollars per share) | $ / shares	$ 44.11
Restricted stock and RSUs expected to vest (shares)	641,209

Stockholder's Equity - Stock-ba

Stockholder's Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 4,154	$ 4,012
Unrecognized compensation cost related to unvested share-based compensation arrangements	27,600
Unrecognized compensation cost, expected recognition period		2 years 3 months 4 days
Share-based compensation expense, capitalized in inventory	300		$ 200
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	219	$ 309
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	368	253
Sales, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,567	$ 3,450

Accumulated Other Comprehensi51

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 400,408
Amounts reclassified from accumulated other comprehensive income to earnings:
Net current-year other comprehensive income (loss)	1,068	$ 762
Ending balance	414,921
Marketable Investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(235)	(105)
Other comprehensive income before reclassifications:
Other comprehensive income before reclassifications	(386)	101
Income tax effect — (expense) benefit	68	0
Net of tax	(318)	101
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized gains — marketable investments	0	(31)
Income tax effect — expense	0	0
Net of tax	0	(31)
Net current-year other comprehensive income (loss)	(318)	70
Ending balance	(553)	(35)
Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	1,804	(4,583)
Other comprehensive income before reclassifications:
Other comprehensive income before reclassifications	1,608	692
Income tax effect — (expense) benefit	(222)	0
Net of tax	1,386	692
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized gains — marketable investments	0	0
Income tax effect — expense	0	0
Net of tax	0	0
Net current-year other comprehensive income (loss)	1,386	692
Ending balance	3,190	(3,891)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	1,569	(4,688)
Other comprehensive income before reclassifications:
Income tax effect — (expense) benefit	(154)	0
Net of tax	1,068	793
Amounts reclassified from accumulated other comprehensive income to earnings:
Realized gains — marketable investments	0	(31)
Income tax effect — expense	0	0
Net of tax	0	(31)
Net current-year other comprehensive income (loss)	1,068	762
Ending balance	$ 2,637	$ (3,926)

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Contingency [Line Items]
Effective tax rate	(43.00%)	(77.40%)
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards, Expiration Period	20 years

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
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income (loss)	$ 5,491	$ (3,106)
Denominator:
Weighted average shares used to compute net (loss) income per share attributable to common stockholders — Basic (in shares)	33,846,142	31,611,841
Potential dilutive shares (in shares)	2,070,909	0
Weighted average shares used to compute net income attributable to common stockholders —Diluted (in shares)	35,917,051	31,611,841
Net (loss) income per share attributable to common stockholders — Basic (in dollars per share)	$ 0.16	$ (0.10)
Net (loss) income per share attributable to common stockholders — Diluted (in dollars per share)	$ 0.15	$ (0.10)

Net Income (Loss) per Share - A

Net Income (Loss) per Share - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	23,900	3,500,000

Revenues - Initial Application

Revenues - Initial Application Period (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Consolidated Balance Sheet Data:
Accounts receivable, net of doubtful accounts	$ 65,107
Inventories	94,616			$ 94,901
Deferred taxes	28,865
Retained earnings	7,951			$ 1,996
Consolidated Income Statement Data:
Revenue	102,701	$ 73,213
Cost of revenue	36,144	25,504
Income (loss) from operations	4,045	(2,046)
Income (loss) before income taxes and equity in losses of unconsolidated investees	4,504
(Benefit from) provision for income taxes	(1,938)	1,355
Net income (loss)	5,491	$ (3,106)
As Reported
Consolidated Balance Sheet Data:
Accounts receivable, net of doubtful accounts	64,327
Inventories	94,891
Deferred taxes	28,993
Retained earnings	7,574
Consolidated Income Statement Data:
Revenue	102,579
Cost of revenue	36,086
Income (loss) from operations	3,981
Income (loss) before income taxes and equity in losses of unconsolidated investees	4,440
(Benefit from) provision for income taxes	(1,910)
Net income (loss)	5,455
Adjustments | Accounting Standards Update 2014-09
Consolidated Balance Sheet Data:
Accounts receivable, net of doubtful accounts	(780)
Inventories	275
Deferred taxes	128
Retained earnings	(377)
Consolidated Income Statement Data:
Revenue	(122)
Cost of revenue	(58)
Income (loss) from operations	(64)
Income (loss) before income taxes and equity in losses of unconsolidated investees	(64)
(Benefit from) provision for income taxes	28
Net income (loss)	$ (36)
Retained Earnings | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of new accounting principle			$ 300

Revenues - Disaggregation of R

Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 102,701	$ 73,213
United States
Disaggregation of Revenue [Line Items]
Revenue	65,801	48,487
Japan
Disaggregation of Revenue [Line Items]
Revenue	10,682	7,642
Other International
Disaggregation of Revenue [Line Items]
Revenue	26,218	17,084
Neuro
Disaggregation of Revenue [Line Items]
Revenue	71,433	50,249
Peripheral Vascular
Disaggregation of Revenue [Line Items]
Revenue	$ 31,268	$ 22,964

Uncategorized Items - pen-20180

Label	Element	Value
Restricted Cash	us-gaap_RestrictedCash	$ 1,704,000
Restricted Cash	us-gaap_RestrictedCash	$ 0