Debt - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense	$ 19,495	$ 8,928	$ 3,681
Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	2,113	2,516	1,097
Amortization of debt discount	10,428	5,405	2,280
Amortization of debt issuance costs	969	724	304
Interest expense	13,510	8,645	3,681
1.75% Convertible Senior Notes due 2023 | Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	2,113	2,516	1,097
Amortization of debt discount	4,735	5,405	2,280
Amortization of debt issuance costs	623	724	304
Interest expense	7,471	8,645	3,681
Convertible Senior Notes due 2025 | Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	0	0	0
Amortization of debt discount	5,693	0	0
Amortization of debt issuance costs	346	0	0
Interest expense	$ 6,039	$ 0	$ 0