Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Amortization of debt issuance costs	$ 1,467	$ 829	$ 28
Amortization of debt discount	15,154	7,646	$ 0
Convertible Senior Notes Due June 2026 | Convertible Debt
Debt Instrument [Line Items]
Contractual interest expense	593
Amortization of debt issuance costs	466
Amortization of debt discount	5,740
Total	6,799
Convertible Senior Notes Due February 2023 | Convertible Debt
Debt Instrument [Line Items]
Contractual interest expense	1,725	1,482
Amortization of debt issuance costs	1,001	829
Amortization of debt discount	9,414	7,646
Total	$ 12,140	$ 9,957