Subsequent Events - Narratives (Details) - Subsequent Event [Member] - USD ($) $ in Millions	Oct. 04, 2019	Oct. 31, 2019
Pfizer Inc. [Member]
Subsequent Event [Line Items]
Upfront license fee receivable	$ 250.0
Ionis [Member]
Subsequent Event [Line Items]
Payment of license fees, milestone payments and royalties, percentage	50.00%
Akcea [Member]
Subsequent Event [Line Items]
Maximum amount of payments receivable for development milestones	$ 205.0
Maximum amount of payments receivable for regulatory milestones	250.0
Maximum amount of payments receivable for commercialization milestones	$ 850.0
Tiered royalties to be received	mid-teens to low twenty percent range on net sales of AKCEA-ANGPTL3-LRx
Akcea [Member] | Ionis [Member]
Subsequent Event [Line Items]
Proceeds from issuance of its common stock	$ 125.0
Akcea [Member] | Maximum [Member]
Subsequent Event [Line Items]
Eligible to receive milestone payment	$ 1,300.0
PTC Therapeutics [Member]
Subsequent Event [Line Items]
License fee receivable		$ 4.0
PTC Therapeutics [Member] | Ionis [Member]
Subsequent Event [Line Items]
Sublicense fee payable		$ 2.4