CONSOLIDATED STATEMENTS OF INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Royalty revenue from a related party \| GSK
Amortization of capitalized fees paid to a related party	$ 3,456	$ 3,456

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

Name:	us-gaap_CapitalizedContractCostAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration