Collaboration Agreements - Royalty Revenues under the Collaboration Agreement with Genentech (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty revenues on ex-U.S. sales	$ 240,275	$ 186,108	$ 455,762	$ 399,827
Collaborative Arrangement with Genentech
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Profits and losses on U.S. commercialization	1,349	2,696	2,404	4,069
Royalty revenues on ex-U.S. sales	$ 1,323	$ 1,546	$ 2,813	$ 2,895

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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