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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Collaboration Agreements (Collaboration Revenues - Merck) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 28, 2018	Dec. 29, 2017	Dec. 30, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 228,602	$ 225,397	$ 186,108	$ 213,719	$ 120,072	$ 152,510	$ 99,008	$ 80,887	$ 853,826	$ 452,477	$ 191,454
Collaborative Arrangement with Merck
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues									$ 0	$ 0	$ 5,000