Convertible Senior Notes - Schedule of Interest Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Amortization of debt discount and issuance costs	$ 33,283	$ 52,733	$ 53,394
2022 Notes
Debt Instrument [Line Items]
Amortization of debt issuance cost	1,606	1,531	860
Amortization of debt discount	$ 31,677	30,159	16,921
Effective interest rate of the liability component (in percent)	4.75%
2018 Notes
Debt Instrument [Line Items]
Amortization of debt issuance cost	$ 0	1,131	1,911
Amortization of debt discount	$ 0	$ 19,912	$ 33,702
Effective interest rate of the liability component (in percent)	6.50%