Fair Value Measurements - Reconciliation of Level 3 Assets and Liabilities (Details) - Royalty Pharma Contingent Milestone Payments - Measured on a recurring basis - Level 3 - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 26, 2020	Sep. 26, 2020
Royalty Pharma Contingent Milestone Payments
Beginning balance	$ 99.0	$ 95.3
Change in fair value	22.2	25.9
Ending balance	$ 121.2	$ 121.2

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant