Convertible Senior Notes - Schedule of Interest Expense Recognized Related to 2023 Notes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Total interest expense related to the 2025 Notes	$ 12,680	$ 5,160	$ 32,780	$ 15,280
Shares of common stock related to convertible senior notes due 2023
Debt Instrument [Line Items]
Amortization of debt discount	2,097	4,759	9,445	14,102
Amortization of debt issuance costs	169	359	745	1,047
Total interest expense related to the 2025 Notes	$ 2,266	$ 5,118	$ 10,190	$ 15,149