Exelixis (EXEL) 10-Q 1 May 19 2019 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 29, 2019	Apr. 22, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 29, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	exel
Entity Registrant Name	EXELIXIS, INC.
Entity Central Index Key	0000939767
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Current Fiscal Year End Date	--01-03
Entity Common Stock, Shares Outstanding		301,767,356

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018	[1]
Current assets:
Cash and cash equivalents	$ 373,937	$ 314,775
Short-term investments	425,713	378,559
Trade and other receivables	107,670	162,771
Other receivables	7,445	16,056
Inventory, net	10,143	9,838
Unbilled collaboration revenue	7,244	0
Prepaid expenses and other current assets	14,146	15,017
Total current assets	946,298	897,016
Long-term investments	218,619	157,187
Long-term restricted cash and investments	1,100	1,100
Property and equipment, net	50,553	50,897
Operating lease right-of-use assets	13,921	5,867
Deferred tax assets, net	243,717	244,111
Goodwill	63,684	63,684
Other long-term assets	3,902	2,424
Total assets	1,541,794	1,422,286
Current liabilities:
Accounts payable	9,748	10,901
Accrued clinical trial liabilities	23,055	18,231
Accrued compensation and benefits	22,550	32,142
Rebates and fees due to customers	19,708	14,954
Accrued collaboration liabilities	7,556	7,419
Current portion of deferred revenue	2,376	0
Other current liabilities	40,139	21,825
Total current liabilities	125,132	105,472
Long-term portion of lease liabilities	19,958	12,178
Long-term portion of deferred revenue	8,323	15,897
Other long-term liabilities	3,361	1,286
Total liabilities	156,774	134,833
Commitments
Stockholders’ equity
Preferred stock, $0.001 par value, 10,000,000 shares authorized and no shares issued	0	0
Common stock, $0.001 par value; 400,000,000 shares authorized; issued and outstanding: 301,519,885 and 299,876,080 at March 31, 2019 and December 31, 2018, respectively	302	300
Additional paid-in capital	2,188,578	2,168,217
Accumulated other comprehensive income (loss)	728	(701)
Accumulated deficit	(804,588)	(880,363)
Total stockholders’ equity	1,385,020	1,287,453
Total liabilities and stockholders’ equity	$ 1,541,794	$ 1,422,286
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 29, 2019	Dec. 28, 2018	[1]
Preferred stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	10,000,000	10,000,000
Shares issued (in shares)	0	0
Common stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	400,000,000	400,000,000
Shares issued (in shares)	301,519,885	299,876,080
Shares outstanding (in shares)	301,519,885	299,876,080
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Total revenues	$ 215,487	$ 213,719
Operating expenses:
Cost of goods sold	7,501	5,639
Research and development	63,289	37,757
Selling, general and administrative	60,138	54,016
Total operating expenses	130,928	97,412
Income from operations	84,559	116,307
Other income (expense), net:
Interest income	6,087	1,895
Other, net	25	169
Total other income (expense), net:	6,112	2,064
Income before income taxes	90,671	118,371
Provision for income taxes	(14,896)	(2,514)
Net income	$ 75,775	$ 115,857
Net income per share, basic (in dollars per share)	$ 0.25	$ 0.39
Net income per share, diluted (in dollars per share)	$ 0.24	$ 0.37
Shares used in computing net income per share, basic (in shares)	300,542	296,421
Shares used in computing net income per share, diluted (in shares)	314,644	313,691
Net product revenues
Total revenues	$ 179,581	$ 134,272
Collaboration revenue
Total revenues	$ 35,906	$ 79,447

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 75,775	$ 115,857
Other comprehensive income (loss):
Net unrealized gains or losses on available-for-sale securities, net of tax impact of $394 and $0, respectively	1,429	(540)
Total other comprehensive income (loss)	1,429	(540)
Comprehensive income	$ 77,204	$ 115,317

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Statement of Comprehensive Income [Abstract]
Unrealized gains or losses on available-for-sale securities, tax impact	$ 394	$ 0
Reclassification adjustments to net income resulting from realized gains or losses on sale of securities	$ 0	$ 0

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total		Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance (in shares) at Dec. 29, 2017			296,209,426
Balance at Dec. 29, 2017	$ 284,961		$ 296	$ 2,114,184	$ (347)	$ (1,829,172)
Net income	115,857					115,857
Other comprehensive income (loss)	(540)				(540)
Issuance of common stock under equity incentive and stock purchase plans (in shares)			484,904
Issuance of common stock under equity incentive and stock purchase plans	1,678		$ 1	1,677
Stock-based compensation	9,305			9,305
Balance (in shares) at Mar. 30, 2018			296,694,330
Balance at Mar. 30, 2018	$ 669,766		$ 297	2,125,166	(887)	(1,454,810)
Balance (in shares) at Dec. 28, 2018	299,876,080	[1]	299,876,080
Balance at Dec. 28, 2018	$ 1,287,453	[1]	$ 300	2,168,217	(701)	(880,363)
Net income	75,775					75,775
Other comprehensive income (loss)	1,429				1,429
Issuance of common stock under equity incentive and stock purchase plans (in shares)			1,643,805
Issuance of common stock under equity incentive and stock purchase plans	7,834		$ 2	7,832
Stock-based compensation	$ 12,529			12,529
Balance (in shares) at Mar. 29, 2019	301,519,885		301,519,885
Balance at Mar. 29, 2019	$ 1,385,020		$ 302	$ 2,188,578	$ 728	$ (804,588)
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 29, 2019	Mar. 30, 2018
Statement of Cash Flows [Abstract]
Net income		$ 75,775	$ 115,857
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		1,962	371
Stock-based compensation expense		12,529	9,305
401(k) matching contributions made in common stock		2,469	1,880
Amortization and other right-of-use assets		(7,730)	0
Gain on other equity investments		0	(209)
Other		(1,415)	(158)
Changes in assets and liabilities:
Trade receivables, net		55,101	(10,819)
Other receivables		8,741	64
Inventory, net		(305)	(906)
Unbilled collaboration revenue		(7,753)	(38,014)
Prepaid expenses and other current assets		871	1,900
Other long-term assets		(4,854)	(346)
Accounts payable		(1,294)	(183)
Accrued compensation and benefits		(9,592)	(317)
Accrued clinical trial liabilities		4,824	(4,498)
Rebates and fees due customers		4,754	4,424
Accrued collaboration liabilities		137	(1,000)
Current and long-term deferred revenue		(1,313)	(2,652)
Long-term portion of lease liabilities		7,517	(35)
Other current and long-term liabilities		21,169	(2,856)
Net cash provided by operating activities		161,593	71,808
Cash flows from investing activities:
Purchases of Property and equipment and other, net		(2,307)	(2,947)
Purchases of investments		(239,869)	(116,537)
Proceeds from maturities of investments		129,820	87,504
Proceeds from sale of investments		4,699	6,238
Proceeds from other equity investments		0	209
Net cash used in investing activities		(107,657)	(25,533)
Cash flows from financing activities:
Proceeds from exercise of stock options		6,817	1,875
Taxes paid related to net share settlement of equity awards		(1,580)	(2,129)
Principal payments on financing lease obligation		(11)	0
Net cash provided by (used in) financing activities		5,226	(254)
Net increase in cash, cash equivalents and restricted cash		59,162	46,021
Cash, cash equivalents and restricted cash at beginning of period		315,875	188,314
Cash, cash equivalents and restricted cash at end of period		375,037	234,335
Supplemental cash flow disclosure
Right-of-use assets obtained in exchange for lease obligations	[1]	8,170	17,180
Unpaid liabilities incurred to acquire Property and equipment		$ 141	$ 6,608
[1]	Amounts for the three months ended March 31, 2019 include receipt of a tenant inventive payment. Amounts for the three months ended March 31, 2018 include the transition adjustment for the adoption of Accounting Standards Codification (ASC) Topic 842, Leases.

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization Exelixis, Inc. (Exelixis, we, our or us) is an oncology-focused biotechnology company that strives to accelerate the discovery, development and commercialization of new medicines for difficult-to-treat cancers. Since we were founded in 1994, four products resulting from our discovery efforts have progressed through clinical development an d received regulatory approval; three have a growing commercial presence in markets worldwide, and we expect that the fourth will soon enter the marketplace in Japan. Two are derived from cabozantinib, an inhibitor of multiple tyrosine kinases including MET, AXL, VEGF receptors and RET. These are: CABOMETYX® (cabozantinib) tablets approved for advanced renal cell carcinoma and previously treated hepatocellular carcinoma and COMETRIQ® (cabozantinib) capsules approved for progressive, metastatic medullary thyroid cancer. The other two products resulting from our discovery efforts are: COTELLIC® (cobimetinib), an inhibitor of MEK, approved as part of a combination regimen to treat a specific form of advanced melanoma and marketed under a collaboration with Genentech, Inc. (a member of the Roche Group) (Genentech); and MINNEBRO™ (esaxerenone), an oral, non-steroidal, selective blocker of the mineralocorticoid receptor, recently approved for the treatment of hypertension in Japan and licensed to Daiichi Sankyo Company, Limited (Daiichi Sankyo). Basis of Consolidation The accompanying Condensed Consolidated Financial Statements include the accounts of Exelixis and those of our wholly-owned subsidiaries. These entities’ functional currency is the U.S. dollar. All intercompany balances and transactions have been eliminated. Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the U.S. for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements. In our opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of our financial statements for the periods presented have been included. We have adopted a 52- or 53-week fiscal year policy that generally ends on the Friday closest to December 31 st . Fiscal year 2019 will end on January 3, 2020 and fiscal year 2018 ended on December 28, 2018. For convenience, references in this report as of and for the fiscal periods ended March 29, 2019 and March 30, 2018, and as of and for the fiscal years ending January 3, 2020 and ended December 28, 2018, are indicated as being as of and for the periods ended March 31, 2019 and March 31, 2018, and the years ending December 31, 2019 and ended December 31, 2018, respectively. Similarly, references in this report to the first day of the fiscal year ended January 3, 2020 are indicated as being as of January 1, 2019. Operating results for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 or for any future period. The accompanying Condensed Consolidated Financial Statements and Notes thereto should be read in conjunction with our Consolidated Financial Statements and Notes thereto for the year ended December 31, 2018 , included in our Annual Report on Form 10-K filed with the SEC on February 22, 2019 . Segment Information We operate in one business segment that focuses on the discovery, development and commercialization of new medicines for difficult-to-treat cancers . Our Chief Executive Officer, as the chief operating decision-maker, manages and allocates resources to our operations on a total consolidated basis. Consistent with this decision-making process, our Chief Executive Officer uses consolidated, single-segment financial information for purposes of evaluating performance, forecasting future period financial results, allocating resources and setting incentive targets. All of our long-lived assets are located in the U.S. See “Note 2. Revenues” for enterprise-wide disclosures about product sales, revenues from major customers and revenues by geographic region. Use of Estimates The preparation of the accompanying Condensed Consolidated Financial Statements conforms to accounting principles generally accepted in the U.S., which requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates including, but not limited to: those related to revenue recognition, including determining the nature and timing of satisfaction of performance obligations, and determining the standalone selling price of performance obligations, and variable consideration such as rebates, chargebacks, sales returns, sales allowances, and milestone payments included in collaboration arrangements; the amounts of revenues and expenses under our profit and loss sharing agreement; the recoverability of inventory; the amounts of operating lease right-of-use assets and lease liabilities; the amounts of deferred tax assets and liabilities including the related valuation allowance; the accrual for certain liabilities including accrued clinical trial liabilities; and valuations of equity awards used to determine stock-based compensation, including certain awards with vesting subject to market or performance conditions. We base our estimates on historical experience and on various other market-specific and other relevant assumptions that we believe 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 sources. Actual results could differ materially from those estimates. Reclassifications Certain prior period amounts in the accompanying Condensed Consolidated Financial Statements have been reclassified to conform to current period presentation. Total revenues and Selling, general and administrative expenses for the three months ended March 31, 2018 have been adjusted to reflect the reclassification of the $1.4 million profit related to the profit-sharing arrangement with Genentech for the commercialization of COTELLIC. In our Condensed Consolidated Financial Statements included in our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, the net profit had been classified as Selling, general and administrative expenses as we expected an overall loss under the agreement for the year ended December 31, 2018. Subsequent to March 31, 2018, we determined that the U.S. commercialization of COTELLIC would result in a profit for the year ended December 31, 2018 and therefore, we had reclassified the profit for the three months ended March 31, 2018 from Selling, general and administrative expenses to Collaboration revenues in our financial statements issued after March 31, 2018. Accordingly, we have also reclassified the profit for the three months ended March 31, 2018 in the accompanying Condensed Consolidated Financial Statements to be consistent with our presentation for the year ended December 31, 2018. For more information on our collaboration agreement with Genentech, see “Note 3. Collaboration Agreements” to our Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2018 . Recently Adopted Accounting Pronouncements On January 1, 2019, we adopted ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220) (ASU 2018-02). There was no financial impact from the adoption of ASU 2018-02 and we did not make an election to reclassify the income tax effects of the Tax Cuts and Jobs Act of 2017 from Accumulated other comprehensive income (loss) to Accumulated deficit. In connection with the adoption of ASU 2018-02, we have adopted the individual unit of account approach for releasing income tax effects from Accumulated other comprehensive income (loss) . On January 1, 2019, we also adopted ASU 2017-08 , Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20) (ASU 2017-08). ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. Specifically, ASU 2017-08 requires the premium to be amortized to the earliest call date. ASU 2017-08 does not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The financial impact from the adoption of ASU 2017-08 was nominal. Recent Accounting Pronouncements Not Yet Adopted In November 2018, the Financial Accounting Standards Board (the FASB) issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). ASU 2018-18 clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the counterparty is a customer for a distinct good or service (i.e. a unit of account). For units of account that are in the scope of Topic 606, all of the guidance in Topic 606 should be applied, including the guidance on recognition, measurement, presentation and disclosure. ASU 2018-18 also adds a reference in Topic 808 to the unit of account guidance in ASC 606 and requires that it be applied only to assess whether transactions in a collaborative arrangement are in the scope of Topic 606. ASU 2018-18 will preclude entities from presenting amounts related to transactions with a counterparty in a collaborative arrangement that is not a customer as revenue from contracts with customers. ASU 2018-18 is effective for us for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We are in the process of assessing the impact of ASU 2018-18 on our Condensed Consolidated Financial Statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Accordingly, ASU 2018-15 requires a customer in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. ASU 2018-15 also requires us to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement, which includes reasonably certain renewals. ASU 2018-15 is effective for us for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We are in the process of assessing the impact of ASU 2018-15 on our Condensed Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04) . ASU 2017-04 eliminated Step 2 from the goodwill impairment test. Instead, under the amendments in ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, an entity should consider income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable. ASU 2017-04 is effective for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We do not expect the adoption of ASU 2017-04 to have a material impact on our Condensed Consolidated Financial Statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) (ASU 2016-13) . ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We do not expect the adoption of ASU 2016-13 to have a material impact on our Condensed Consolidated Financial Statements.

Revenues

Revenues	3 Months Ended
	Mar. 29, 2019
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES Revenues by disaggregated category were as follows (in thousands): Three Months Ended March 31, 2019 2018 Product revenues: Gross product revenues $ 223,750 $ 159,436 Discounts and allowances (44,169 ) (25,164 ) Net product revenues 179,581 134,272 Collaboration revenues: License revenues (1) 24,509 69,030 Research and development service revenues (2) 11,928 10,099 Other collaboration revenues (3) (531 ) 318 Total collaboration revenues 35,906 79,447 Total revenues $ 215,487 $ 213,719 ____________________ (1) License revenues included the immediate recognition of the portion of milestones allocated to the transfer of intellectual property licenses for which it had become probable in the current period that the milestone would be achieved and a significant revenue reversal would not occur, as well as royalty revenues from Ipsen Pharma SAS (Ipsen) and Genentech. (2) Research and development service revenues included the recognition of deferred revenue for the portion of upfront and milestone payments that have been allocated to research and development service performance obligations, as well as development cost reimbursements earned on our collaboration agreements. (3) Other collaboration revenues included the profit on the U.S. commercialization of COTELLIC from Genentech and revenues on product supply services provided to Ipsen and Takeda Pharmaceutical Company Ltd. (Takeda), which were partially offset by the 3% royalty we are required to pay GlaxoSmithKline (GSK) on the net sales by Ipsen of any product incorporating cabozantinib. Net product revenues, License revenues and Research and development services revenues were recorded in accordance with Topic 606 for all periods presented. Net product revenues and License revenues related to goods and intellectual property licenses transferred at a point in time and Research and development services revenues related to services performed over time. Other collaboration revenues, which included the p rofit on the U.S. commercialization of COTELLIC and net losses on product supply services, were recorded in accordance with ASC Topic 808, Collaborative Arrangements for all periods presented . Net product revenues disaggregated by product were as follows (in thousands): Three Months Ended March 31, 2019 2018 CABOMETYX $ 175,890 $ 128,934 COMETRIQ 3,691 5,338 Net product revenues $ 179,581 $ 134,272 Total revenues disaggregated by significant customer were as follows (dollars in thousands): Three Months Ended March 31, 2019 2018 Dollars Percent of total Dollars Percent of total Caremark L.L.C. $ 32,698 15 % $ 26,388 12 % Affiliates of McKesson Corporation 25,311 12 % 21,331 10 % Accredo Health, Incorporated 22,495 10 % 18,286 9 % Affiliates of AmerisourceBergen Corporation 21,902 10 % 15,736 7 % Ipsen 21,868 10 % 53,809 25 % Others, individually less than 10% of Total revenues for all periods presented 91,213 43 % 78,169 37 % Total revenues $ 215,487 100 % $ 213,719 100 % Total revenues disaggregated by geographic region were as follows (in thousands): Three Months Ended March 31, 2019 2018 U.S. $ 182,126 $ 136,993 Europe 21,868 53,809 Rest of the world 11,493 22,917 Total revenues $ 215,487 $ 213,719 Net product revenues are attributed to geographic region based on the ship-to location. Collaboration revenues are attributed to geographic region based on the location of our collaboration partners’ headquarters. Product Sales Discounts and Allowances The activities and ending reserve balances for each significant category of discounts and allowances (which constitute variable consideration) were as follows (in thousands): Chargebacks and Discounts for Prompt Payment Other Customer Credits/Fees and Co-pay Assistance Rebates Returns Total Balance at December 31, 2018 $ 2,322 $ 3,038 $ 11,916 $ — $ 17,276 Provision related to sales made in: Current period 27,153 3,875 12,905 — 43,933 Prior periods — 9 227 — 236 Payments and customer credits issued (27,367 ) (4,189 ) (8,073 ) — (39,629 ) Balance at March 31, 2019 $ 2,108 $ 2,733 $ 16,975 $ — $ 21,816 Chargebacks and discounts for prompt payment are recorded as a reduction of trade receivables and the remaining reserve balances are classified as Other current liabilities in the accompanying Condensed Consolidated Balance Sheets. Contract Assets and Liabilities We receive payments from our licensees based on billing schedules established in each contract. Amounts are recorded as accounts receivable when our right to consideration is unconditional. Upfront and milestone payments may require deferral of revenue recognition to a future period until we perform our obligations under these arrangements and are recorded as deferred revenue upon receipt or when due. We may also recognize revenue in advance of the contractual billing schedule and such amounts are recorded as unbilled collaboration revenue when recognized. Changes in our contract assets and liabilities under Topic 606 were as follows (in thousands): Contract Assets: Unbilled Collaboration Revenue Contract Liabilities: Deferred Revenue Current Portion Long-term Portion Current Portion Long-term Portion Balance at December 31, 2018 $ — $ — $ — $ 15,897 Increases as a result of a change in transaction price and recognition of revenues as services are performed 10,222 1,450 — — Transfer to receivables from contract assets recognized at the beginning of the period (543 ) — — — Increases as a result of the deferral of milestones achieved in period, excluding amounts recognized as revenue — — — — Revenue recognized that was included in the contract liability balance at the beginning of the period — — (1,313 ) — Other adjustments (1) (2,435 ) (1,450 ) 3,689 (7,574 ) Balance at March 31, 2019 $ 7,244 $ — $ 2,376 $ 8,323 ____________________ (1) Includes reclassification of deferred revenue from long-term to current and adjustments made due to netting of contract assets and liabilities by collaboration agreement. During the three months ended March 31, 2019 and 2018 , we recognized $25.3 million and $71.3 million , respectively, in revenues under Topic 606 for performance obligations satisfied in previous periods. Such revenues primarily related to milestone and royalty payments allocated to our license performance obligations of our collaborations with Ipsen, Takeda and Bristol-Myers Squibb Company (BMS).

Collaboration Agreements

Collaboration Agreements	3 Months Ended
	Mar. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
COLLABORATION AGREEMENTS	COLLABORATION AGREEMENTS We have established multiple collaborations with leading pharmaceutical companies for the commercialization and further development of cabozantinib, as well as with smaller, discovery-focused biotechnology companies to expand our product pipeline. Additionally, in line with our business strategy prior to the commercialization of our first product, COMETRIQ, we entered into other collaborations with leading pharmaceutical companies including Genentech, Daiichi Sankyo and BMS for other compounds and programs in our portfolio. See “Note 3. Collaboration Agreements” to our Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2018 for a description of each of our collaboration agreements. Under these collaborations, we are generally entitled to receive milestone and royalty payments, and for certain collaborations, payments for product supply services, development cost reimbursements, and/or profit-sharing payments. See “Note 2. Revenues” for information on collaboration revenues recognized during the three months ended March 31, 2019 and 2018 . Cabozantinib Commercial Collaborations Ipsen Collaboration In February 2016, we entered into a collaboration and license agreement with Ipsen for the commercialization and further development of cabozantinib. Pursuant to the terms of the collaboration agreement, Ipsen received exclusive commercialization rights for current and potential future cabozantinib indications outside of the U.S., Canada and Japan. The collaboration agreement was subsequently amended in December 2016 to include commercialization rights in Canada. We have also agreed to collaborate with Ipsen on the development of cabozantinib for current and potential future indications. Collaboration revenues under the collaboration agreement with Ipsen were as follows (in thousands): Three Months Ended March 31, 2019 2018 Ipsen collaboration revenues $ 21,868 $ 53,809 As of March 31, 2019 , $46.8 million of the transaction price allocated to our research and development services performance obligation had not been satisfied. As of March 31, 2019 , the net contract liability for the collaboration agreement with Ipsen was $10.7 million , of which 2.4 million was included in the Current portion of deferred revenue and $8.3 million was included in the Long-term portion of deferred revenue in the accompanying Condensed Consolidated Balance Sheets. Takeda Collaboration In January 2017, we entered into a collaboration and license agreement with Takeda. See “Note 11. Subsequent Events - Amendment to Collaboration Agreement with Takeda” for information regarding an amendment to our collaboration agreement with Takeda. Pursuant to this collaboration agreement, Takeda has exclusive commercialization rights for current and potential future cabozantinib indications in Japan, and the parties have agreed to collaborate on the clinical development of cabozantinib in Japan. Collaboration revenues under the collaboration agreement with Takeda were as follows (in thousands): Three Months Ended March 31, 2019 2018 Takeda collaboration revenues $ 11,493 $ 2,917 As of March 31, 2019 , $25.2 million of the transaction price allocated to our research and development services performance obligation had not been satisfied. As of March 31, 2019 , the net contract asset for the collaboration agreement with Takeda was $7.2 million , which was included in Unbilled collaboration revenue in the accompanying Condensed Consolidated Balance Sheets. GlaxoSmithKline (GSK) In October 2002, we established a product development and commercialization collaboration agreement with GSK. Under the terms of the collaboration agreement, GSK had the right to choose cabozantinib for further development and commercialization, but notified us in October 2008 that it had waived its right to select the compound for such activities. Although the collaboration agreement was terminated in December 2014, GSK continues to be entitled to a 3% royalty we are required to pay on all net sales of any product incorporating cabozantinib by us and our collaboration partners. Royalties accruing to GSK in connection with the sales of cabozantinib are included in Cost of goods sold for sales by us and as a reduction of Collaboration revenues for sales by Ipsen. Such royalties accruing to GSK were as follows (in thousands): Three Months Ended March 31, 2019 2018 Royalties accruing to GSK $ 7,282 $ 5,125 Genentech Collaboration In December 2006, we out-licensed the development and commercialization of cobimetinib to Genentech pursuant to a worldwide collaboration agreement. Under the terms of the collaboration agreement, we developed cobimetinib through the determination of the maximum tolerated dose in a phase 1 clinical trial, and Genentech had the option to co-develop cobimetinib, an option that Genentech exercised, and in March 2009, we granted to Genentech an exclusive worldwide revenue-bearing license to cobimetinib, at which point Genentech became responsible for completing the phase 1 clinical trial and the subsequent clinical development. In November 2015, the U.S. Food and Drug Administration approved cobimetinib, under the brand name COTELLIC, in combination with Genentech’s Zelboraf (vemurafenib) as a treatment for patients with BRAF V600E or V600K mutation-positive advanced melanoma. COTELLIC in combination with Zelboraf has also been approved in the European Union and multiple additional countries for use in the same indication. Profits on U.S. commercialization and Royalty revenues on ex-U.S. sales were as follows (in thousands): Three Months Ended March 31, 2019 2018 Profits on U.S. commercialization $ 1,055 $ 1,373 Royalty revenues on ex-U.S. sales $ 1,490 $ 1,349

Cash and Investments

Cash and Investments	3 Months Ended
	Mar. 29, 2019
Investments, Debt and Equity Securities [Abstract]
CASH AND INVESTMENTS	CASH AND INVESTMENTS Cash, Cash Equivalents and Restricted Cash A reconciliation of Cash, cash equivalents, and restricted cash reported within our Condensed Consolidated Balance Sheets to the amount reported within the accompanying Condensed Consolidated Statements of Cash Flows was as follows (in thousands): March 31, 2019 December 31, 2018 March 31, 2018 December 31, 2017 Cash and cash equivalents $ 373,937 $ 314,775 $ 232,331 $ 183,164 Restricted cash included in short-term restricted cash and investments — — 504 504 Restricted cash included in long-term restricted cash and investments 1,100 1,100 1,500 4,646 Cash, cash equivalents, and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows $ 375,037 $ 315,875 $ 234,335 $ 188,314 Restricted cash includes certificates of deposit used to collateralize letters of credit and, in prior periods, a purchasing card program. Cash and Investments Cash and investments by security type were as follows (in thousands): March 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Investments available-for-sale: Money market funds $ 75,171 $ — $ — $ 75,171 Commercial paper 414,317 — — 414,317 Corporate bonds 417,303 1,257 (175 ) 418,385 U.S. Treasury and government sponsored enterprises 84,448 41 (2 ) 84,487 Total investments available-for-sale 991,239 1,298 (177 ) 992,360 Cash and restricted cash 1,019 — — 1,019 Certificates of deposit 25,990 — — 25,990 Total cash and investments $ 1,018,248 $ 1,298 $ (177 ) $ 1,019,369 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Investments available-for-sale: Money market funds $ 47,744 $ — $ — $ 47,744 Commercial paper 381,134 — (1 ) 381,133 Corporate bonds 344,741 180 (857 ) 344,064 U.S. Treasury and government sponsored enterprises 55,224 2 (25 ) 55,201 Total investments available-for-sale 828,843 182 (883 ) 828,142 Cash and restricted cash 6,883 — — 6,883 Certificates of deposit 16,596 — — 16,596 Total cash and investments $ 852,322 $ 182 $ (883 ) $ 851,621 Gains and losses on the sales of investments available-for-sale were nominal during the three months ended March 31, 2019 and 2018 . The fair value and gross unrealized losses on investments available-for-sale in an unrealized loss position were as follows (in thousands): March 31, 2019 In an Unrealized Loss Position Less than 12 Months In an Unrealized Loss Position 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross Corporate bonds $ 49,233 $ (39 ) $ 45,010 $ (136 ) $ 94,243 $ (175 ) U.S. Treasury and government sponsored enterprises — — 7,990 (2 ) 7,990 (2 ) Total $ 49,233 $ (39 ) $ 53,000 $ (138 ) $ 102,233 $ (177 ) December 31, 2018 In an Unrealized Loss Position Less than 12 Months In an Unrealized Loss Position 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross Corporate bonds $ 236,162 $ (606 ) $ 39,627 $ (251 ) $ 275,789 $ (857 ) U.S. Treasury and government sponsored enterprises 28,105 (16 ) 9,182 (9 ) 37,287 (25 ) Commercial paper 7,091 (1 ) — — 7,091 (1 ) Total $ 271,358 $ (623 ) $ 48,809 $ (260 ) $ 320,167 $ (883 ) There were 69 and 199 investments in an unrealized loss position as of March 31, 2019 and December 31, 2018 , respectively. During the three months ended March 31, 2019 and 2018 we did no t record any other-than-temporary impairment charges on our available-for-sale securities. Based upon our quarterly impairment review, we determined that the unrealized losses were not attributed to credit risk, but were primarily associated with changes in interest rates. Based on the scheduled maturities of our investments and our determination that it was more likely than not that we will hold these investments for a period of time sufficient for a recovery of our cost basis, we concluded that the unrealized losses in our investment securities were not other-than-temporary. The fair value of investments available-for-sale by contractual maturity were as follows (in thousands): March 31, December 31, 2018 Maturing in one year or less $ 784,432 $ 674,455 Maturing after one year through five years 207,928 153,687 Total investments available-for-sale $ 992,360 $ 828,142 Related Party Transactions BlackRock, Inc. (BlackRock), a global provider of investment, advisory and risk management solutions, reported that as of December 31, 2018 , the most recent date for which they reported ownership data, their beneficial ownership was more than 10% of our outstanding common stock. BlackRock manages a portion of our cash and investments portfolio. As of March 31, 2019 and December 31, 2018 , respectively, the fair value of cash and investments managed by BlackRock was $356.0 million and $298.5 million , which included $0.8 million and $3.0 million invested in the BlackRock Liquidity Money Market Fund. We incurred $0.1 million in fees for BlackRock advisory services performed during the three months ended March 31, 2019 .

Inventory

Inventory	3 Months Ended
	Mar. 29, 2019
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in thousands): March 31, December 31, 2018 Raw materials $ 2,245 $ 1,922 Work in process 6,514 6,170 Finished goods 4,862 3,836 Total $ 13,621 $ 11,928 Balance Sheet classification: Current portion included in Inventory $ 10,143 $ 9,838 Long-term portion included in Other long-term assets 3,478 2,090 Total $ 13,621 $ 11,928 Write-downs related to excess and expiring inventory are charged to Cost of goods sold or the cost of supplied product included in Collaboration revenues . Such write-downs were $0.2 million for the three months ended March 31, 2019 . There were no such write-downs for the three months ended and March 31, 2018 . Inventory not expected to be used in production or sold in the next 12 months is classified as Other long-term assets in the accompanying Condensed Consolidated Balance Sheets. As of both March 31, 2019 and December 31, 2018 , the long-term portion of inventory consisted of portions of our raw materials and finished goods, and as March 31, 2019 , also a portion of our work in process.

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 29, 2019
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment consisted of the following (in thousands): March 31, December 31, Leasehold improvements $ 33,811 $ 33,941 Computer equipment and software 15,110 15,022 Furniture and fixtures 12,908 12,709 Laboratory equipment 6,764 5,668 Construction in progress 1,231 866 69,824 68,206 Less: accumulated depreciation and amortization (19,271 ) (17,309 ) Property and equipment, net $ 50,553 $ 50,897 Depreciation expense was $2.0 million and $0.4 million for the three months ended March 31, 2019 and 2018 , respectively.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 29, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION We allocated the stock-based compensation expense for our equity incentive plans and our 2000 Employee Stock Purchase Plan (ESPP) as follows (in thousands): Three Months Ended March 31, 2019 2018 Research and development $ 4,306 $ 3,033 Selling, general and administrative 8,223 6,272 Total stock-based compensation $ 12,529 $ 9,305 We have several equity incentive plans under which we have granted stock options and restricted stock units (RSUs) to employees and directors. At March 31, 2019 , 14,586,459 shares were available for grant under our equity incentive plans. We used a Monte Carlo simulation pricing model to value stock options that include market vesting conditions and a Black-Scholes Merton option pricing model to value other stock options and ESPP purchases. The weighted average grant-date fair value per share of stock options and ESPP purchases were as follows: Three Months Ended March 31, 2019 2018 Stock options $ 9.21 $ 11.52 ESPP $ 4.67 $ 7.39 The grant-date fair value of stock option grants and ESPP purchases was estimated using the following assumptions: Three Months Ended March 31, 2019 2018 Stock options: Risk-free interest rate 2.22 % 2.40 % Dividend yield — % — % Volatility 49 % 54 % Expected life 4.0 years 4.0 years ESPP: Risk-free interest rate 2.48 % 1.53 % Dividend yield — % — % Volatility 57 % 53 % Expected life 6 months 6 months We considered our implied volatility and our historical volatility in developing our estimates of expected volatility. The assumptions for the expected life of stock options were based on historical exercise patterns and post-vesting termination behavior. The risk-free interest rate is based on U.S. Treasury rates with the same or similar term as the underlying award. Our dividend rate is based on historical experience and our investors’ current expectations. The fair value of RSUs was based on the closing price of the underlying common stock on the date of grant. Activity for stock options during the three months ended March 31, 2019 was as follows (dollars in thousands , except per share amounts): Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Options outstanding at December 31, 2018 22,674,062 $ 8.71 Granted 246,820 $ 22.94 Exercised (1,413,766 ) $ 4.91 Forfeited (44,200 ) $ 14.32 Expired (22,925 ) $ 22.12 Options outstanding at March 31, 2019 21,439,991 $ 9.10 3.6 years $ 317,143 Exercisable at March 31, 2019 15,714,721 $ 6.01 2.9 years $ 280,307 As of March 31, 2019 , there was $44.1 million of unrecognized compensation expense related to our unvested stock options. The compensation expense for the unvested stock options will be recognized over a weighted-average period of 2.5 years . Activity for RSUs during the three months ended March 31, 2019 was as follows (dollars in thousands , except per share amounts): Shares Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value RSUs outstanding at December 31, 2018 4,857,334 $ 18.42 Awarded 123,410 $ 22.94 Vested and released (194,296 ) $ 7.83 Forfeited (100,630 ) $ 18.13 RSUs outstanding at March 31, 2019 4,685,818 $ 18.98 2.0 years $ 111,522 During 2018, in connection with our long-term incentive compensation program, we awarded 693,131 RSUs that will vest upon the achievement of certain product revenue, late-stage clinical development and pipeline expansion performance targets (PSUs). The PSUs were designed to drive the performance of our management team toward the achievement of key corporate objectives and will be forfeited if the performance targets are not met by December 31, 2021. Expense recognition for PSUs commences when it is determined that attainment of the performance goal is probable. As of March 31, 2019 , we have not recognized any compensation expense related to these PSUs and the total unrecognized compensation expense was $12.7 million . As of March 31, 2019 , there was $77.0 million of unrecognized compensation expense related to our unvested RSUs, including the PSUs described above. The compensation expense for the unvested RSUs will be recognized over a weighted-average period of 2.9 years .

Income Taxes

Income Taxes	3 Months Ended
	Mar. 29, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective income tax rate was 16.4% during the three months ended March 31, 2019 as compared to 2.1% for the three months ended March 31, 2018 . The Provision for income taxes relating to our pre-tax income for the three months ended March 31, 2018 was largely offset by a valuation allowance against our net operating loss carryforwards and other deferred tax assets. At December 31, 2018, we released substantially all of our valuation allowance against our deferred tax assets, after we determined that it was more likely than not that these deferred tax assets would be realized. The effective tax rate for the three months ended March 31, 2019 differed from the U.S. federal statutory rate of 21% primarily was due to excess tax benefits related to the exercise of certain stock options during the quarter.

Net Income Per Share

Net Income Per Share	3 Months Ended
	Mar. 29, 2019
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE The computation of basic and diluted net income per share was as follows (in thousands, except per share amounts): Three Months Ended March 31, 2019 2018 Numerator: Net income $ 75,775 $ 115,857 Denominator: Weighted-average shares of common stock outstanding used in computing basic net income per share 300,542 296,421 Dilutive securities 14,102 17,270 Weighted-average shares of common stock outstanding and dilutive securities used in computing diluted net income per share 314,644 313,691 Net income per share, basic $ 0.25 $ 0.39 Net income per share, diluted $ 0.24 $ 0.37 Dilutive securities include outstanding stock options, unvested RSUs and ESPP contributions. Potential shares of common stock not included in the computation of diluted net income per share because to do so would be anti-dilutive was as follows (in thousands): Three Months Ended March 31, 2019 2018 Potentially dilutive securities 5,089 1,907

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 29, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The classification within the fair value hierarchy of our financial assets that were measured and recorded at fair value on a recurring basis was as follows (in thousands): March 31, 2019 Level 1 Level 2 Total Money market funds $ 75,171 $ — $ 75,171 Commercial paper — 414,317 414,317 Corporate bonds — 418,385 418,385 U.S. Treasury and government sponsored enterprises — 84,487 84,487 Total investments available-for-sale 75,171 917,189 992,360 Certificates of deposit — 25,990 25,990 Total financial assets carried at fair value $ 75,171 $ 943,179 $ 1,018,350 December 31, 2018 Level 1 Level 2 Total Money market funds $ 47,744 $ — $ 47,744 Commercial paper — 381,133 381,133 Corporate bonds — 344,064 344,064 U.S. Treasury and government sponsored enterprises — 55,201 55,201 Total investments available-for-sale 47,744 780,398 828,142 Certificates of deposit — 16,596 16,596 Total financial assets carried at fair value $ 47,744 $ 796,994 $ 844,738 We did not have any financial liabilities measured and recorded at fair value on a recurring basis as of March 31, 2019 or December 31, 2018 . We did not have any financial assets or liabilities classified as Level 3 in the fair value hierarchy as of March 31, 2019 or December 31, 2018 . There were no transfers of financial assets or liabilities between Levels 1, 2 and 3 during the three months ended March 31, 2019 or 2018 . When available, we value investments based on quoted prices for those financial instruments, which is a Level 1 input. Our remaining investments are valued using third-party pricing sources, which use observable market prices, interest rates and yield curves observable at commonly quoted intervals for similar assets as observable inputs for pricing, which is a Level 2 input. See “Note 11. Commitments” to our Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2018 for a description of the determination of the amount of our operating lease liabilities. Our remaining financial assets and liabilities include cash and restricted cash, Trade receivables, net, Other receivables, Accounts payable, Accrued compensation and benefits, Accrued clinical trial liabilities, Accrued collaboration liabilities, Rebates and fees due to customers and other current and long-term liabilities. Those financial assets and liabilities are carried at cost which approximates their fair values.

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 29, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENT	SUBSEQUENT EVENTS Lease Amendment On April 1, 2019, we entered into an amendment to the existing Lease Agreement (the Lease) relating to our corporate headquarters located at 1851, 1801, and 1751 Harbor Bay Parkway, Alameda, California (the Premises). The Lease Amendment provides, among other things, for the (i) expansion of the Premises by 37,544 square feet of office facilities located at 1601 Harbor Bay Parkway, Alameda, California (the 1601 Expansion Space) and (ii) surrender of 2,703 square feet of office facilities located at 1751 Harbor Bay Parkway, Alameda, California (the 1751 Space). We surrendered the 1751 Space on April 15, 2019 and the term for the 1601 Expansion Space will begin ninety days after the landlord’s delivery of the entire 1601 Expansion Space (the 1601 Expansion Space Commencement Date). The term for the 1601 Expansion Space is expected to commence on December 1, 2019, and will run coterminous with the term of the Lease for the existing space, which ends on January 31, 2028. We have been provided an allowance of $1.7 million for tenant improvements to the 1601 Expansion Space. Following April 15, 2019, the monthly base rent for the Premises, other than the 1601 Expansion Space, is $224,505 through January 31, 2020, increasing throughout the remainder of the term to $283,933 at the end of the term. Following the 1601 Expansion Space Commencement Date, the monthly base rent for the 1601 Expansion Space will be $71,334 through November 30, 2020, increasing throughout the remainder of the term to $90,481 at the end of the term. The aggregate contractual base rent for the entire 169,606 square feet of the Premises from April 15, 2019, through the remainder of the Lease term will be approximately $34.6 million . In addition, we are required to pay the landlord for certain operating expenses and taxes they incur related to the Premises. Amendment to Collaboration Agreement with Takeda On April 29, 2019, we executed an amendment to our January 2017 collaboration agreement with Takeda (the Amendment), which will become effective on May 7, 2019. The Amendment, among other things, reduces the amount of reimbursements we will receive from Takeda for costs associated with our required global pharmacovigilance activities and limits those reimbursements to $1.0 million per year. It also increases the total potential development, regulatory and first-sale milestone payments to be paid to us by Takeda for second-line renal cell carcinoma (RCC) , first-line RCC and second-line hepatocellular carcinoma by an aggregate of $12.0 million to $102.0 million , including an increase from $10.0 million to $16.0 million for the milestone we expect to receive for the April 2019 submission of a regulatory application for cabozantinib as a treatment for patients with advanced RCC to the Japanese Ministry of Health, Labour and Welfare. We continue to be eligible to receive additional development, regulatory and first-sale milestone payments for other potential future indications. The Amendment also increases the amount of Takeda’s potential sales-based milestones by an aggregate of $3.0 million to $86.0 million . We continue to be eligible to receive royalties on net sales of cabozantinib in Japan.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Consolidation	Basis of Consolidation The accompanying Condensed Consolidated Financial Statements include the accounts of Exelixis and those of our wholly-owned subsidiaries. These entities’ functional currency is the U.S. dollar. All intercompany balances and transactions have been eliminated.
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the U.S. for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements. In our opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of our financial statements for the periods presented have been included.
Fiscal Period	We have adopted a 52- or 53-week fiscal year policy that generally ends on the Friday closest to December 31 st . Fiscal year 2019 will end on January 3, 2020 and fiscal year 2018 ended on December 28, 2018. For convenience, references in this report as of and for the fiscal periods ended March 29, 2019 and March 30, 2018, and as of and for the fiscal years ending January 3, 2020 and ended December 28, 2018, are indicated as being as of and for the periods ended March 31, 2019 and March 31, 2018, and the years ending December 31, 2019 and ended December 31, 2018, respectively.
Segment Information	Segment Information We operate in one business segment that focuses on the discovery, development and commercialization of new medicines for difficult-to-treat cancers . Our Chief Executive Officer, as the chief operating decision-maker, manages and allocates resources to our operations on a total consolidated basis. Consistent with this decision-making process, our Chief Executive Officer uses consolidated, single-segment financial information for purposes of evaluating performance, forecasting future period financial results, allocating resources and setting incentive targets. All of our long-lived assets are located in the U.S.
Use of Estimates	Use of Estimates The preparation of the accompanying Condensed Consolidated Financial Statements conforms to accounting principles generally accepted in the U.S., which requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates including, but not limited to: those related to revenue recognition, including determining the nature and timing of satisfaction of performance obligations, and determining the standalone selling price of performance obligations, and variable consideration such as rebates, chargebacks, sales returns, sales allowances, and milestone payments included in collaboration arrangements; the amounts of revenues and expenses under our profit and loss sharing agreement; the recoverability of inventory; the amounts of operating lease right-of-use assets and lease liabilities; the amounts of deferred tax assets and liabilities including the related valuation allowance; the accrual for certain liabilities including accrued clinical trial liabilities; and valuations of equity awards used to determine stock-based compensation, including certain awards with vesting subject to market or performance conditions. We base our estimates on historical experience and on various other market-specific and other relevant assumptions that we believe 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 sources. Actual results could differ materially from those estimates.
Reclassifications	Reclassifications Certain prior period amounts in the accompanying Condensed Consolidated Financial Statements have been reclassified to conform to current period presentation.
Recently Adopted Accounting Pronouncements and Recent Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements On January 1, 2019, we adopted ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220) (ASU 2018-02). There was no financial impact from the adoption of ASU 2018-02 and we did not make an election to reclassify the income tax effects of the Tax Cuts and Jobs Act of 2017 from Accumulated other comprehensive income (loss) to Accumulated deficit. In connection with the adoption of ASU 2018-02, we have adopted the individual unit of account approach for releasing income tax effects from Accumulated other comprehensive income (loss) . On January 1, 2019, we also adopted ASU 2017-08 , Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20) (ASU 2017-08). ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. Specifically, ASU 2017-08 requires the premium to be amortized to the earliest call date. ASU 2017-08 does not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The financial impact from the adoption of ASU 2017-08 was nominal. Recent Accounting Pronouncements Not Yet Adopted In November 2018, the Financial Accounting Standards Board (the FASB) issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). ASU 2018-18 clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the counterparty is a customer for a distinct good or service (i.e. a unit of account). For units of account that are in the scope of Topic 606, all of the guidance in Topic 606 should be applied, including the guidance on recognition, measurement, presentation and disclosure. ASU 2018-18 also adds a reference in Topic 808 to the unit of account guidance in ASC 606 and requires that it be applied only to assess whether transactions in a collaborative arrangement are in the scope of Topic 606. ASU 2018-18 will preclude entities from presenting amounts related to transactions with a counterparty in a collaborative arrangement that is not a customer as revenue from contracts with customers. ASU 2018-18 is effective for us for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We are in the process of assessing the impact of ASU 2018-18 on our Condensed Consolidated Financial Statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Accordingly, ASU 2018-15 requires a customer in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. ASU 2018-15 also requires us to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement, which includes reasonably certain renewals. ASU 2018-15 is effective for us for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We are in the process of assessing the impact of ASU 2018-15 on our Condensed Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04) . ASU 2017-04 eliminated Step 2 from the goodwill impairment test. Instead, under the amendments in ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, an entity should consider income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable. ASU 2017-04 is effective for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We do not expect the adoption of ASU 2017-04 to have a material impact on our Condensed Consolidated Financial Statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) (ASU 2016-13) . ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We do not expect the adoption of ASU 2016-13 to have a material impact on our Condensed Consolidated Financial Statements.
Revenue	Chargebacks and discounts for prompt payment are recorded as a reduction of trade receivables and the remaining reserve balances are classified as Other current liabilities in the accompanying Condensed Consolidated Balance Sheets. Contract Assets and Liabilities We receive payments from our licensees based on billing schedules established in each contract. Amounts are recorded as accounts receivable when our right to consideration is unconditional. Upfront and milestone payments may require deferral of revenue recognition to a future period until we perform our obligations under these arrangements and are recorded as deferred revenue upon receipt or when due. We may also recognize revenue in advance of the contractual billing schedule and such amounts are recorded as unbilled collaboration revenue when recognized. Net product revenues, License revenues and Research and development services revenues were recorded in accordance with Topic 606 for all periods presented. Net product revenues and License revenues related to goods and intellectual property licenses transferred at a point in time and Research and development services revenues related to services performed over time. Other collaboration revenues, which included the p rofit on the U.S. commercialization of COTELLIC and net losses on product supply services, were recorded in accordance with ASC Topic 808, Collaborative Arrangements for all periods presented . Net product revenues are attributed to geographic region based on the ship-to location. Collaboration revenues are attributed to geographic region based on the location of our collaboration partners’ headquarters.

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 29, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Revenues by disaggregated category were as follows (in thousands): Three Months Ended March 31, 2019 2018 Product revenues: Gross product revenues $ 223,750 $ 159,436 Discounts and allowances (44,169 ) (25,164 ) Net product revenues 179,581 134,272 Collaboration revenues: License revenues (1) 24,509 69,030 Research and development service revenues (2) 11,928 10,099 Other collaboration revenues (3) (531 ) 318 Total collaboration revenues 35,906 79,447 Total revenues $ 215,487 $ 213,719 ____________________ (1) License revenues included the immediate recognition of the portion of milestones allocated to the transfer of intellectual property licenses for which it had become probable in the current period that the milestone would be achieved and a significant revenue reversal would not occur, as well as royalty revenues from Ipsen Pharma SAS (Ipsen) and Genentech. (2) Research and development service revenues included the recognition of deferred revenue for the portion of upfront and milestone payments that have been allocated to research and development service performance obligations, as well as development cost reimbursements earned on our collaboration agreements. (3) Other collaboration revenues included the profit on the U.S. commercialization of COTELLIC from Genentech and revenues on product supply services provided to Ipsen and Takeda Pharmaceutical Company Ltd. (Takeda), which were partially offset by the 3% royalty we are required to pay GlaxoSmithKline (GSK) on the net sales by Ipsen of any product incorporating cabozantinib. Net product revenues, License revenues and Research and development services revenues were recorded in accordance with Topic 606 for all periods presented. Net product revenues and License revenues related to goods and intellectual property licenses transferred at a point in time and Research and development services revenues related to services performed over time. Other collaboration revenues, which included the p rofit on the U.S. commercialization of COTELLIC and net losses on product supply services, were recorded in accordance with ASC Topic 808, Collaborative Arrangements for all periods presented . Net product revenues disaggregated by product were as follows (in thousands): Three Months Ended March 31, 2019 2018 CABOMETYX $ 175,890 $ 128,934 COMETRIQ 3,691 5,338 Net product revenues $ 179,581 $ 134,272 Total revenues disaggregated by significant customer were as follows (dollars in thousands): Three Months Ended March 31, 2019 2018 Dollars Percent of total Dollars Percent of total Caremark L.L.C. $ 32,698 15 % $ 26,388 12 % Affiliates of McKesson Corporation 25,311 12 % 21,331 10 % Accredo Health, Incorporated 22,495 10 % 18,286 9 % Affiliates of AmerisourceBergen Corporation 21,902 10 % 15,736 7 % Ipsen 21,868 10 % 53,809 25 % Others, individually less than 10% of Total revenues for all periods presented 91,213 43 % 78,169 37 % Total revenues $ 215,487 100 % $ 213,719 100 % Total revenues disaggregated by geographic region were as follows (in thousands): Three Months Ended March 31, 2019 2018 U.S. $ 182,126 $ 136,993 Europe 21,868 53,809 Rest of the world 11,493 22,917 Total revenues $ 215,487 $ 213,719
Activities and Ending Reserve Balances for Significant Categories of Discounts and Allowances	The activities and ending reserve balances for each significant category of discounts and allowances (which constitute variable consideration) were as follows (in thousands): Chargebacks and Discounts for Prompt Payment Other Customer Credits/Fees and Co-pay Assistance Rebates Returns Total Balance at December 31, 2018 $ 2,322 $ 3,038 $ 11,916 $ — $ 17,276 Provision related to sales made in: Current period 27,153 3,875 12,905 — 43,933 Prior periods — 9 227 — 236 Payments and customer credits issued (27,367 ) (4,189 ) (8,073 ) — (39,629 ) Balance at March 31, 2019 $ 2,108 $ 2,733 $ 16,975 $ — $ 21,816
Contract Assets and Liabilities under Topic 606	Changes in our contract assets and liabilities under Topic 606 were as follows (in thousands): Contract Assets: Unbilled Collaboration Revenue Contract Liabilities: Deferred Revenue Current Portion Long-term Portion Current Portion Long-term Portion Balance at December 31, 2018 $ — $ — $ — $ 15,897 Increases as a result of a change in transaction price and recognition of revenues as services are performed 10,222 1,450 — — Transfer to receivables from contract assets recognized at the beginning of the period (543 ) — — — Increases as a result of the deferral of milestones achieved in period, excluding amounts recognized as revenue — — — — Revenue recognized that was included in the contract liability balance at the beginning of the period — — (1,313 ) — Other adjustments (1) (2,435 ) (1,450 ) 3,689 (7,574 ) Balance at March 31, 2019 $ 7,244 $ — $ 2,376 $ 8,323 ____________________ (1) Includes reclassification of deferred revenue from long-term to current and adjustments made due to netting of contract assets and liabilities by collaboration agreement.

Collaboration Agreements (Table

Collaboration Agreements (Tables)	3 Months Ended
	Mar. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Collaborative Revenues Under Collaboration Agreement	Profits on U.S. commercialization and Royalty revenues on ex-U.S. sales were as follows (in thousands): Three Months Ended March 31, 2019 2018 Profits on U.S. commercialization $ 1,055 $ 1,373 Royalty revenues on ex-U.S. sales $ 1,490 $ 1,349 Collaboration revenues under the collaboration agreement with Ipsen were as follows (in thousands): Three Months Ended March 31, 2019 2018 Ipsen collaboration revenues $ 21,868 $ 53,809 Collaboration revenues under the collaboration agreement with Takeda were as follows (in thousands): Three Months Ended March 31, 2019 2018 Takeda collaboration revenues $ 11,493 $ 2,917

Cash and Investments (Tables)

Cash and Investments (Tables)	3 Months Ended
	Mar. 29, 2019
Investments, Debt and Equity Securities [Abstract]
Reconciliation of Cash, Cash Equivalents, and Restricted Cash	A reconciliation of Cash, cash equivalents, and restricted cash reported within our Condensed Consolidated Balance Sheets to the amount reported within the accompanying Condensed Consolidated Statements of Cash Flows was as follows (in thousands): March 31, 2019 December 31, 2018 March 31, 2018 December 31, 2017 Cash and cash equivalents $ 373,937 $ 314,775 $ 232,331 $ 183,164 Restricted cash included in short-term restricted cash and investments — — 504 504 Restricted cash included in long-term restricted cash and investments 1,100 1,100 1,500 4,646 Cash, cash equivalents, and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows $ 375,037 $ 315,875 $ 234,335 $ 188,314
Reconciliation of Cash, Cash Equivalents, and Restricted Cash	A reconciliation of Cash, cash equivalents, and restricted cash reported within our Condensed Consolidated Balance Sheets to the amount reported within the accompanying Condensed Consolidated Statements of Cash Flows was as follows (in thousands): March 31, 2019 December 31, 2018 March 31, 2018 December 31, 2017 Cash and cash equivalents $ 373,937 $ 314,775 $ 232,331 $ 183,164 Restricted cash included in short-term restricted cash and investments — — 504 504 Restricted cash included in long-term restricted cash and investments 1,100 1,100 1,500 4,646 Cash, cash equivalents, and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows $ 375,037 $ 315,875 $ 234,335 $ 188,314
Investments by Security Type	Cash and investments by security type were as follows (in thousands): March 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Investments available-for-sale: Money market funds $ 75,171 $ — $ — $ 75,171 Commercial paper 414,317 — — 414,317 Corporate bonds 417,303 1,257 (175 ) 418,385 U.S. Treasury and government sponsored enterprises 84,448 41 (2 ) 84,487 Total investments available-for-sale 991,239 1,298 (177 ) 992,360 Cash and restricted cash 1,019 — — 1,019 Certificates of deposit 25,990 — — 25,990 Total cash and investments $ 1,018,248 $ 1,298 $ (177 ) $ 1,019,369 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Investments available-for-sale: Money market funds $ 47,744 $ — $ — $ 47,744 Commercial paper 381,134 — (1 ) 381,133 Corporate bonds 344,741 180 (857 ) 344,064 U.S. Treasury and government sponsored enterprises 55,224 2 (25 ) 55,201 Total investments available-for-sale 828,843 182 (883 ) 828,142 Cash and restricted cash 6,883 — — 6,883 Certificates of deposit 16,596 — — 16,596 Total cash and investments $ 852,322 $ 182 $ (883 ) $ 851,621
Fair Value and Gross Unrealized Losses of Investments Available-for-Sale in an Unrealized Loss Position	The fair value and gross unrealized losses on investments available-for-sale in an unrealized loss position were as follows (in thousands): March 31, 2019 In an Unrealized Loss Position Less than 12 Months In an Unrealized Loss Position 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross Corporate bonds $ 49,233 $ (39 ) $ 45,010 $ (136 ) $ 94,243 $ (175 ) U.S. Treasury and government sponsored enterprises — — 7,990 (2 ) 7,990 (2 ) Total $ 49,233 $ (39 ) $ 53,000 $ (138 ) $ 102,233 $ (177 ) December 31, 2018 In an Unrealized Loss Position Less than 12 Months In an Unrealized Loss Position 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross Corporate bonds $ 236,162 $ (606 ) $ 39,627 $ (251 ) $ 275,789 $ (857 ) U.S. Treasury and government sponsored enterprises 28,105 (16 ) 9,182 (9 ) 37,287 (25 ) Commercial paper 7,091 (1 ) — — 7,091 (1 ) Total $ 271,358 $ (623 ) $ 48,809 $ (260 ) $ 320,167 $ (883 )
Fair Value of Cash Equivalents and Investments by Contractual Maturity	The fair value of investments available-for-sale by contractual maturity were as follows (in thousands): March 31, December 31, 2018 Maturing in one year or less $ 784,432 $ 674,455 Maturing after one year through five years 207,928 153,687 Total investments available-for-sale $ 992,360 $ 828,142

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 29, 2019
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in thousands): March 31, December 31, 2018 Raw materials $ 2,245 $ 1,922 Work in process 6,514 6,170 Finished goods 4,862 3,836 Total $ 13,621 $ 11,928 Balance Sheet classification: Current portion included in Inventory $ 10,143 $ 9,838 Long-term portion included in Other long-term assets 3,478 2,090 Total $ 13,621 $ 11,928

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 29, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands): March 31, December 31, Leasehold improvements $ 33,811 $ 33,941 Computer equipment and software 15,110 15,022 Furniture and fixtures 12,908 12,709 Laboratory equipment 6,764 5,668 Construction in progress 1,231 866 69,824 68,206 Less: accumulated depreciation and amortization (19,271 ) (17,309 ) Property and equipment, net $ 50,553 $ 50,897

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 29, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Allocated Employee Stock-Based Compensation Expense	We allocated the stock-based compensation expense for our equity incentive plans and our 2000 Employee Stock Purchase Plan (ESPP) as follows (in thousands): Three Months Ended March 31, 2019 2018 Research and development $ 4,306 $ 3,033 Selling, general and administrative 8,223 6,272 Total stock-based compensation $ 12,529 $ 9,305
Weighted Average Grant-Date Fair Value of Stock Options and ESPP Purchases	The weighted average grant-date fair value per share of stock options and ESPP purchases were as follows: Three Months Ended March 31, 2019 2018 Stock options $ 9.21 $ 11.52 ESPP $ 4.67 $ 7.39
Valuation Assumptions Used to Estimate Grant-Date Fair Value	The grant-date fair value of stock option grants and ESPP purchases was estimated using the following assumptions: Three Months Ended March 31, 2019 2018 Stock options: Risk-free interest rate 2.22 % 2.40 % Dividend yield — % — % Volatility 49 % 54 % Expected life 4.0 years 4.0 years ESPP: Risk-free interest rate 2.48 % 1.53 % Dividend yield — % — % Volatility 57 % 53 % Expected life 6 months 6 months
Stock Option Activity	Activity for stock options during the three months ended March 31, 2019 was as follows (dollars in thousands , except per share amounts): Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Options outstanding at December 31, 2018 22,674,062 $ 8.71 Granted 246,820 $ 22.94 Exercised (1,413,766 ) $ 4.91 Forfeited (44,200 ) $ 14.32 Expired (22,925 ) $ 22.12 Options outstanding at March 31, 2019 21,439,991 $ 9.10 3.6 years $ 317,143 Exercisable at March 31, 2019 15,714,721 $ 6.01 2.9 years $ 280,307
RSU Activity	Activity for RSUs during the three months ended March 31, 2019 was as follows (dollars in thousands , except per share amounts): Shares Weighted Average Grant Date Fair Value Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value RSUs outstanding at December 31, 2018 4,857,334 $ 18.42 Awarded 123,410 $ 22.94 Vested and released (194,296 ) $ 7.83 Forfeited (100,630 ) $ 18.13 RSUs outstanding at March 31, 2019 4,685,818 $ 18.98 2.0 years $ 111,522

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Mar. 29, 2019
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Income Per Share	The computation of basic and diluted net income per share was as follows (in thousands, except per share amounts): Three Months Ended March 31, 2019 2018 Numerator: Net income $ 75,775 $ 115,857 Denominator: Weighted-average shares of common stock outstanding used in computing basic net income per share 300,542 296,421 Dilutive securities 14,102 17,270 Weighted-average shares of common stock outstanding and dilutive securities used in computing diluted net income per share 314,644 313,691 Net income per share, basic $ 0.25 $ 0.39 Net income per share, diluted $ 0.24 $ 0.37
Potential Shares of Common Stock Not Included in the Computation of Diluted Net Income (Loss) Per Share	Potential shares of common stock not included in the computation of diluted net income per share because to do so would be anti-dilutive was as follows (in thousands): Three Months Ended March 31, 2019 2018 Potentially dilutive securities 5,089 1,907

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 29, 2019
Fair Value Disclosures [Abstract]
Classification of Financial Assets Measured and Recorded at Fair Value on a Recurring Basis	The classification within the fair value hierarchy of our financial assets that were measured and recorded at fair value on a recurring basis was as follows (in thousands): March 31, 2019 Level 1 Level 2 Total Money market funds $ 75,171 $ — $ 75,171 Commercial paper — 414,317 414,317 Corporate bonds — 418,385 418,385 U.S. Treasury and government sponsored enterprises — 84,487 84,487 Total investments available-for-sale 75,171 917,189 992,360 Certificates of deposit — 25,990 25,990 Total financial assets carried at fair value $ 75,171 $ 943,179 $ 1,018,350 December 31, 2018 Level 1 Level 2 Total Money market funds $ 47,744 $ — $ 47,744 Commercial paper — 381,133 381,133 Corporate bonds — 344,064 344,064 U.S. Treasury and government sponsored enterprises — 55,201 55,201 Total investments available-for-sale 47,744 780,398 828,142 Certificates of deposit — 16,596 16,596 Total financial assets carried at fair value $ 47,744 $ 796,994 $ 844,738

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended
	Mar. 29, 2019USD ($)segmentproduct	Mar. 30, 2018USD ($)
Organization And Summary Of Significant Policies [Line Items]
Number of products that entered in the commercial marketplace	4
Number of business segments | segment	1
Selling, general and administrative | $	$ 60,138	$ 54,016
Restatement Adjustment
Organization And Summary Of Significant Policies [Line Items]
Selling, general and administrative | $		$ (1,400)
Commercial Presence in Markets Worldwide
Organization And Summary Of Significant Policies [Line Items]
Number of products that entered in the commercial marketplace	3
Products Derived from Cabozantinib
Organization And Summary Of Significant Policies [Line Items]
Number of products that entered in the commercial marketplace	2

Revenues - Revenues by Disaggre

Revenues - Revenues by Disaggregated Category (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 215,487	$ 213,719
Collaborative Arrangement with Ipsen
Disaggregation of Revenue [Line Items]
Total revenues	$ 21,868	53,809
GSK | Collaborative Arrangement with Ipsen
Disaggregation of Revenue [Line Items]
Percent of royalty on net sale	3.00%
Net product revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 179,581	134,272
Gross product revenues
Disaggregation of Revenue [Line Items]
Total revenues	223,750	159,436
Discounts and allowances
Disaggregation of Revenue [Line Items]
Total revenues	44,169	25,164
Total collaboration revenues
Disaggregation of Revenue [Line Items]
Total revenues	35,906	79,447
License revenues
Disaggregation of Revenue [Line Items]
Total revenues	24,509	69,030
Research and development services revenues
Disaggregation of Revenue [Line Items]
Total revenues	11,928	10,099
Other collaboration revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ (531)	$ 318

Revenues - Net Product Revenues

Revenues - Net Product Revenues Disaggregated by Product (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Disaggregation of Revenue [Line Items]
Net product revenues	$ 215,487	$ 213,719
Net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	179,581	134,272
CABOMETYX
Disaggregation of Revenue [Line Items]
Net product revenues	175,890	128,934
COMETRIQ
Disaggregation of Revenue [Line Items]
Net product revenues	$ 3,691	$ 5,338

Revenues - Revenues Disaggregat

Revenues - Revenues Disaggregated by Significant Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 215,487	$ 213,719
Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	100.00%	100.00%
Caremark L.L.C.
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 32,698	$ 26,388
Caremark L.L.C. | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	15.00%	12.00%
Affiliates of McKesson Corporation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 25,311	$ 21,331
Affiliates of McKesson Corporation | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	12.00%	10.00%
Accredo Health, Incorporated
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 22,495	$ 18,286
Accredo Health, Incorporated | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	10.00%	9.00%
Affiliates of AmerisourceBergen Corporation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 21,902	$ 15,736
Affiliates of AmerisourceBergen Corporation | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	10.00%	7.00%
Ipsen
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 21,868	$ 53,809
Ipsen | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	10.00%	25.00%
Others, individually less than 10% of Total revenues for all periods presented
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 91,213	$ 78,169
Others, individually less than 10% of Total revenues for all periods presented | Revenue | Customer Concentration Risk
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percent of total revenues	43.00%	37.00%

Revenues - Revenues Disaggreg_2

Revenues - Revenues Disaggregated by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 215,487	$ 213,719
U.S.
Disaggregation of Revenue [Line Items]
Total revenues	182,126	136,993
Europe
Disaggregation of Revenue [Line Items]
Total revenues	21,868	53,809
Rest of the world
Disaggregation of Revenue [Line Items]
Total revenues	$ 11,493	$ 22,917

Revenues - Activities and Endin

Revenues - Activities and Ending Reserve Balances for Significant Categories of Discounts and Allowances (Details) $ in Thousands	3 Months Ended
	Mar. 29, 2019USD ($)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at December 31, 2018	$ 17,276
Provision related to sales made in:
Current period	43,933
Prior periods	236
Payments and customer credits issued	(39,629)
Balance at March 31, 2019	21,816
Chargebacks and Discounts for Prompt Payment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at December 31, 2018	2,322
Provision related to sales made in:
Current period	27,153
Prior periods	0
Payments and customer credits issued	(27,367)
Balance at March 31, 2019	2,108
Other Customer Credits/Fees and Co-pay Assistance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at December 31, 2018	3,038
Provision related to sales made in:
Current period	3,875
Prior periods	9
Payments and customer credits issued	(4,189)
Balance at March 31, 2019	2,733
Rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at December 31, 2018	11,916
Provision related to sales made in:
Current period	12,905
Prior periods	227
Payments and customer credits issued	(8,073)
Balance at March 31, 2019	16,975
Returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at December 31, 2018	0
Provision related to sales made in:
Current period	0
Prior periods	0
Payments and customer credits issued	0
Balance at March 31, 2019	$ 0

Revenues - Changes in Contract

Revenues - Changes in Contract Assets and Liabilities under Topic 606 (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 29, 2019	Mar. 30, 2018
Contract Assets - Current Portion
Balance	[1]	$ 0
Increases as a result of a change in transaction price and recognition of revenues as services are performed		10,222
Transfer to receivables from contract assets recognized at the beginning of the period		(543)
Other		(2,435)
Balance		7,244
Contract Assets - Long-term Portion
Increases as a result of a change in transaction price and recognition of revenues as services are performed		1,450
Other		(1,450)
Balance		0
Contract Liabilities - Current Portion
Balance	[1]	0
Increases as a result of the deferral of milestones achieved in period, excluding amounts recognized as revenue		0
Revenue recognized that was included in the contract liability balance at the beginning of the period		(1,313)
Other		3,689
Balance		2,376
Contract Liabilities - Long-term Portion
Balance	[1]	15,897
Increases as a result of the deferral of milestones achieved in period, excluding amounts recognized as revenue		0
Other		(7,574)
Balance		8,323
Revenues recognized for performance obligations satisfied in previous periods		25,300	$ 71,300
Balances Without the Adoption of Topic 606
Contract Assets - Current Portion
Balance		0
Contract Assets - Long-term Portion
Balance		0
Contract Liabilities - Current Portion
Balance		0
Contract Liabilities - Long-term Portion
Balance		$ 15,897
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Collaboration Agreements - Coll

Collaboration Agreements - Collaboration Revenues under the Collaboration Agreement with Ipsen (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 215,487	$ 213,719
Collaborative Arrangement with Ipsen
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 21,868	$ 53,809

Collaboration Agreements - Ipse

Collaboration Agreements - Ipsen Collaboration (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018	[1]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net contract liability, current portion of deferred revenue	$ 2,376	$ 0
Net contract liability, long-term portion of deferred revenue	8,323	$ 15,897
Collaborative Arrangement with Ipsen
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Remaining performance obligation	46,800
Net contract liability	10,700
Net contract liability, current portion of deferred revenue	2,400
Net contract liability, long-term portion of deferred revenue	$ 8,300
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Collaboration Agreements - Co_2

Collaboration Agreements - Collaboration Revenues under the Collaboration Agreement with Takeda (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 215,487	$ 213,719
Collaborative Arrangement with Takeda
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 11,493	$ 2,917

Collaboration Agreements - Take

Collaboration Agreements - Takeda Collaboration (Details) - Collaborative Arrangement with Takeda $ in Millions	Mar. 29, 2019USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Remaining performance obligation	$ 25.2
Net contract liability	$ 7.2

Collaboration Agreements - Roya

Collaboration Agreements - Royalty Revenues under the Collaboration Agreement with GSK (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Collaboration Agreement with GlaxoSmithKline
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalties accruing to GSK	$ 7,282	$ 5,125
GSK | Collaborative Arrangement with Ipsen
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percent of royalty on net sale	3.00%

Collaboration Agreements - Ro_2

Collaboration Agreements - Royalty Revenues under the Collaboration Agreement with Genentech (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty revenues on ex-U.S. sales	$ 215,487	$ 213,719
COTELLIC | Collaborative Arrangement with Genentech
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty revenues on ex-U.S. sales	1,490	1,349
Profits and losses on U.S. commercialization	$ 1,055	$ 1,373

Cash and Investments - Reconcil

Cash and Investments - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018		Mar. 30, 2018	Dec. 29, 2017
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 373,937	$ 314,775	[1]	$ 232,331	$ 183,164
Restricted cash included in short-term restricted cash and investments	0	0	[1]	504	504
Restricted cash included in long-term restricted cash and investments	1,100	1,100	[1]	1,500	4,646
Cash, cash equivalents, and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows	$ 375,037	$ 315,875		$ 234,335	$ 188,314
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Cash and Investments - Investme

Cash and Investments - Investments by Security Type (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018	Mar. 30, 2018	Dec. 29, 2017
Investment [Line Items]
Amortized Cost	$ 991,239	$ 828,843
Amortized Cost	375,037	315,875	$ 234,335	$ 188,314
Gross Unrealized Gains	1,298	182
Gross Unrealized Losses	(177)	(883)
Fair Value	992,360	828,142
Total cash and investments, amortized cost	1,018,248	852,322
Total cash and investments, fair value	1,019,369	851,621
Money market funds
Investment [Line Items]
Amortized Cost	75,171	47,744
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	75,171	47,744
Commercial paper
Investment [Line Items]
Amortized Cost	414,317	381,134
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Fair Value	414,317	381,133
Corporate bonds
Investment [Line Items]
Amortized Cost	417,303	344,741
Gross Unrealized Gains	1,257	180
Gross Unrealized Losses	(175)	(857)
Fair Value	418,385	344,064
U.S. Treasury and government sponsored enterprises
Investment [Line Items]
Amortized Cost	84,448	55,224
Gross Unrealized Gains	41	2
Gross Unrealized Losses	(2)	(25)
Fair Value	84,487	55,201
Cash and restricted cash
Investment [Line Items]
Amortized Cost	1,019	6,883
Fair Value	1,019	6,883
Certificates of deposit
Investment [Line Items]
Amortized Cost	25,990	16,596
Fair Value	$ 25,990	$ 16,596

Cash and Investments - Fair Val

Cash and Investments - Fair Value and Gross Unrealized Losses of Investments Available-for-Sale in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018
Fair Value
In an Unrealized Loss Position Less than 12 Months	$ 49,233	$ 271,358
In an Unrealized Loss Position 12 Months or Greater	53,000	48,809
Total	102,233	320,167
Gross Unrealized Losses
In an Unrealized Loss Position Less than 12 Months	(39)	(623)
In an Unrealized Loss Position 12 Months or Greater	(138)	(260)
Total	(177)	(883)
U.S. Treasury and government sponsored enterprises
Fair Value
In an Unrealized Loss Position Less than 12 Months	0	28,105
In an Unrealized Loss Position 12 Months or Greater	7,990	9,182
Total	7,990	37,287
Gross Unrealized Losses
In an Unrealized Loss Position Less than 12 Months	0	(16)
In an Unrealized Loss Position 12 Months or Greater	(2)	(9)
Total	(2)	(25)
Corporate bonds
Fair Value
In an Unrealized Loss Position Less than 12 Months	49,233	236,162
In an Unrealized Loss Position 12 Months or Greater	45,010	39,627
Total	94,243	275,789
Gross Unrealized Losses
In an Unrealized Loss Position Less than 12 Months	(39)	(606)
In an Unrealized Loss Position 12 Months or Greater	(136)	(251)
Total	$ (175)	(857)
Commercial paper
Fair Value
In an Unrealized Loss Position Less than 12 Months		7,091
In an Unrealized Loss Position 12 Months or Greater		0
Total		7,091
Gross Unrealized Losses
In an Unrealized Loss Position Less than 12 Months		(1)
In an Unrealized Loss Position 12 Months or Greater		0
Total		$ (1)

Cash and Investments - Narrativ

Cash and Investments - Narrative (Details)	3 Months Ended		9 Months Ended
	Mar. 29, 2019USD ($)investment	Mar. 30, 2018USD ($)	Sep. 28, 2018USD ($)	Dec. 28, 2018USD ($)investment
Investments, Debt and Equity Securities [Abstract]
Gain (loss) on sales of investments available-for-sale	$ 0	$ 0
Number of investments in an unrealized loss position | investment	69			199
Other-than-temporary impairment charges on available-for-sale securities	$ 0	$ 0
Beneficial ownership interest by BlackRock (more than)	10.00%
Fair value of cash and investments managed by BlackRock	$ 356,000,000			$ 298,500,000
Fair value of cash and investments managed by BlackRock in the BlackRock Liquidity Money Market Fund	$ 800,000			$ 3,000,000
Fees for advisory services paid to BlackRock			$ 100,000

Cash and Investments - Fair V_2

Cash and Investments - Fair Value of Cash Equivalents and Investments by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$ 784,432	$ 674,455
Maturing after one year through five years	207,928	153,687
Total	$ 992,360	$ 828,142

Inventory (Details)

Inventory (Details) - USD ($)	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018	Dec. 28, 2018
Inventory [Line Items]
Raw materials	$ 2,245,000		$ 1,922,000
Work in process	6,514,000		6,170,000
Finished goods	4,862,000		3,836,000
Total	13,621,000		11,928,000
Write-downs on inventory	200,000	$ 0
Current portion included in Inventory
Inventory [Line Items]
Total	10,143,000		9,838,000
Long-term portion included in Other long-term assets
Inventory [Line Items]
Total	$ 3,478,000		$ 2,090,000

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 69,824	$ 68,206
Less: accumulated depreciation and amortization	(19,271)	(17,309)
Property and equipment, net	50,553	50,897	[1]
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	33,811	33,941
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,110	15,022
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,908	12,709
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,764	5,668
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,231	$ 866
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2018 has been derived from the audited financial statements as of that date.

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 2	$ 0.4

Stock-Based Compensation - Allo

Stock-Based Compensation - Allocated Employee Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 12,529	$ 9,305
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	4,306	3,033
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 8,223	$ 6,272

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 29, 2019USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares) | shares	14,586,459
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense | $	$ 44.1
Weighted-average cost recognition period	2 years 5 months 26 days
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense | $	$ 12.7
RSUs awarded (in shares) | shares	693,131
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense | $	$ 77
Weighted-average cost recognition period	2 years 11 months 1 day
RSUs awarded (in shares) | shares	123,410

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted Average Grant-Date Fair Value of Stock Options and ESPP Purchases (Details) - $ / shares	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value (in dollars per share)	$ 9.21	$ 11.52
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value (in dollars per share)	$ 4.67	$ 7.39

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions Used to Estimate Grant-Date Fair Value (Details)	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.22%	2.40%
Dividend yield	0.00%	0.00%
Expected volatility	49.00%	54.00%
Expected life	3 years 11 months 19 days	3 years 11 months 23 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.48%	1.53%
Dividend yield	0.00%	0.00%
Expected volatility	57.00%	53.00%
Expected life	6 months	6 months

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 29, 2019USD ($)$ / sharesshares
Shares
Options outstanding at beginning of period (in shares) | shares	22,674,062
Granted (in shares) | shares	246,820
Exercised (in shares) | shares	(1,413,766)
Forfeited (in shares) | shares	(44,200)
Expired (in shares) | shares	(22,925)
Options outstanding at end of period (in shares) | shares	21,439,991
Exercisable at end of period (in shares) | shares	15,714,721
Weighted Average Exercise Price Per Share
Options outstanding at beginning of period (in dollars per share) | $ / shares	$ 8.71
Granted (in dollars per share) | $ / shares	22.94
Exercised (in dollars per share) | $ / shares	4.91
Forfeited (in dollars per share) | $ / shares	14.32
Expired (in dollars per share) | $ / shares	22.12
Options outstanding at end of period (in dollars per share) | $ / shares	9.10
Exercisable at end of period (in dollars per share) | $ / shares	$ 6.01
Weighted Average Remaining Contractual Term
Options outstanding at end of period	3 years 7 months 13 days
Exercisable at end of period	2 years 10 months 24 days
Aggregate Intrinsic Value
Options outstanding at end of period | $	$ 317,143
Exercisable at end of period | $	$ 280,307

Stock-Based Compensation - RSU

Stock-Based Compensation - RSU Activity (Details) - RSUs $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 29, 2019USD ($)$ / sharesshares
Shares
RSUs outstanding at beginning of period (in shares) | shares	4,857,334
Awarded (in shares) | shares	123,410
Vested and released (in shares) | shares	(194,296)
Forfeited (in shares) | shares	(100,630)
RSUs outstanding at end of period (in shares) | shares	4,685,818
Weighted Average Grant Date Fair Value Per Share
RSUs outstanding at beginning of period (in dollars per share) | $ / shares	$ 18.42
Awarded (in dollars per share) | $ / shares	22.94
Vested and released (in dollars per share) | $ / shares	7.83
Forfeited (in dollars per share) | $ / shares	18.13
RSUs outstanding at end of period (in dollars per share) | $ / shares	$ 18.98
Weighted Average Remaining Contractual Term
RSUs outstanding at end of period	2 years
Aggregate Intrinsic Value
RSUs outstanding at end of period | $	$ 111,522

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	16.40%	2.10%
Provision for income taxes	$ 14,896	$ 2,514

Net Income Per Share - Computat

Net Income Per Share - Computation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Numerator:
Net income	$ 75,775	$ 115,857
Denominator:
Weighted-average shares of common stock outstanding used in computing basic net income per share (in shares)	300,542	296,421
Dilutive securities (in shares)	14,102	17,270
Weighted-average shares of common stock outstanding and dilutive securities used in computing diluted net income per share (in shares)	314,644	313,691
Net income per share, basic (in dollars per share)	$ 0.25	$ 0.39
Net income per share, diluted (in dollars per share)	$ 0.24	$ 0.37

Net Income Per Share - Potentia

Net Income Per Share - Potential Shares of Common Stock Not Included in the Computation of Diluted Net Income (Loss) Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Potentially dilutive securities
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares (in shares)	5,089	1,907

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 28, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	$ 992,360	$ 828,142
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	992,360	828,142
Financial assets	1,018,350	844,738
Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	75,171	47,744
Financial assets	75,171	47,744
Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	917,189	780,398
Financial assets	943,179	796,994
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	75,171	47,744
Money market funds | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	75,171	47,744
Money market funds | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	75,171	47,744
Money market funds | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	0	0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	414,317	381,133
Commercial paper | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	414,317	381,133
Commercial paper | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	0	0
Commercial paper | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	414,317	381,133
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	418,385	344,064
Corporate bonds | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	418,385	344,064
Corporate bonds | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	0	0
Corporate bonds | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	418,385	344,064
U.S. Treasury and government sponsored enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	84,487	55,201
U.S. Treasury and government sponsored enterprises | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	84,487	55,201
U.S. Treasury and government sponsored enterprises | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	0	0
U.S. Treasury and government sponsored enterprises | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	84,487	55,201
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certificates of deposit	25,990	16,596
Certificates of deposit | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certificates of deposit	25,990	16,596
Certificates of deposit | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certificates of deposit	0	0
Certificates of deposit | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certificates of deposit	$ 25,990	$ 16,596

Subsequent Event (Details)

Subsequent Event (Details)	Apr. 29, 2019USD ($)	Apr. 15, 2019USD ($)ft²	Dec. 28, 2018USD ($)	Apr. 01, 2019USD ($)ft²
Collaborative Arrangement with Takeda
Subsequent Event [Line Items]
Milestone payments earned			$ 10,000,000
Subsequent Event | Collaborative Arrangement with Takeda
Subsequent Event [Line Items]
Limit on reimbursement per year	$ 1,000,000
Increase in maximum amount eligible for development and regulatory milestones	12,000,000
Maximum amount eligible for development and regulatory milestones	102,000,000
Milestone payments earned	16,000,000
Increase in maximum amount eligible for commercial milestones under collaborations agreement	3,000,000
Maximum amount eligible for commercial milestones under collaborations agreement	$ 86,000,000
Subsequent Event | Corporate Headquarters, Alameda, California
Subsequent Event [Line Items]
Operating lease, expansion (in square feet) | ft²				37,544
Operating lease, surrendered (in square feet) | ft²				2,703
Tenant improvement allowance				$ 1,700,000
Area of lease property (in square feet) | ft²		169,606
Aggregate contractual base rent		$ 34,600,000
Subsequent Event | Corporate Headquarters, Alameda, California | Minimum
Subsequent Event [Line Items]
Monthly base rent		224,505
Operating lease, not yet commenced, monthly base rent		71,334
Subsequent Event | Corporate Headquarters, Alameda, California | Maximum
Subsequent Event [Line Items]
Monthly base rent		283,933
Operating lease, not yet commenced, monthly base rent		$ 90,481

Uncategorized Items - exel-2019

Label	Element	Value
Accounting Standards Update 2016-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 258,505,000
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 258,505,000