Debt - Schedule of Interest Expense (Details) - Convertible Notes and 2027 Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Contractual interest expense	$ 35,383	$ 40,151	$ 11,406
Amortization of debt issuance costs	1,670	4,663	4,050
Amortization of debt discount	8,272	34,228	34,039
Interest expense	$ 45,325	$ 79,042	$ 49,495