Collaborative Arrangements and Acquisitions - Cystic Fibrosis Foundation Therapeutics Incorporated (Details) - Cystic Fibrosis Foundation Therapeutics Incorporated - USD ($)	1 Months Ended	9 Months Ended
Oct. 31, 2016	Sep. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payments		$ 0
Collaborative funding	$ 75,000,000
Additional collaborative funding	$ 6,000,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration