Debt - Convertible Senior Notes (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)	Mar. 25, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 20, 2020 USD ($)	Jul. 23, 2018 USD ($)
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 23,512
Net Carrying Amount	$ 23,243		$ 22,482
1.75% Convertible Senior Notes due 2023 | Senior Notes
Debt Instrument [Line Items]
Stated Cash Interest Rate	1.75%
Effective Interest Rate	2.45%
Conversion Rate	32.7332
Aggregate Principal Amount	$ 23,512		25,626		$ 143,750
Repurchased face amount	120,238
Unamortized Debt Discount	0		2,776
Unamortized Debt Issuance Costs	269		368
Net Carrying Amount	23,243		22,482
0% Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Aggregate Principal Amount	661,250
Net Carrying Amount	$ 650,093		488,268
0% Convertible Senior Notes due 2025 | Senior Notes
Debt Instrument [Line Items]
Effective Interest Rate	0.42%
Conversion Rate	13.7920
Aggregate Principal Amount	$ 661,250		661,250	$ 661,250
Unamortized Debt Discount	0		163,077
Unamortized Debt Issuance Costs	11,157		9,905
Net Carrying Amount	650,093		488,268
0.5% Convertible Senior Notes Due 2027
Debt Instrument [Line Items]
Aggregate Principal Amount	575,000
Net Carrying Amount	$ 562,674		$ 0
0.5% Convertible Senior Notes Due 2027 | Senior Notes
Debt Instrument [Line Items]
Stated Cash Interest Rate	0.50%
Effective Interest Rate	0.90%
Conversion Rate	10.6920
Aggregate Principal Amount	$ 575,000	$ 575,000
Unamortized Debt Discount	0
Unamortized Debt Issuance Costs	12,326
Net Carrying Amount	$ 562,674