Investment in Viking - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018	Apr. 30, 2016	Aug. 31, 2014
Variable Interest Entity [Line Items]
Loss recorded (as a percent)	12.40%
Investment in Viking common stock		$ 48,400		$ 46,200
Warrants		1,500
Exercise price of warrants (USD per share)						$ 125.08
Warrants investments in Viking		58,335		55,448
Equity Method Investee
Variable Interest Entity [Line Items]
Increase (decrease) in equity method investment			$ 2,700
Exercise price of warrants (USD per share)					$ 1.50
Warrants
Variable Interest Entity [Line Items]
Warrants investments in Viking		$ 9,900		$ 9,300
Viking Therapeutics, Inc.
Variable Interest Entity [Line Items]
Ownership interest (as a percent)		10.30%