Convertible Debt (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Apr. 30, 2021	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Convertible Debt [Abstract]
Repurchase of convertible notes					$ 256,963	$ 0
Cost of call spread	$ 46,900	$ 52,600
Purchase of note hedges	136,700	108,700			136,620	0
Proceeds from issuance of warrants	89,800	$ 56,100			89,752	0
Loss on early retirement of debt			$ (8,627)	$ 0	(8,627)	$ 0
0% Notes [Member]
Convertible Debt [Abstract]
Face amount of offering	632,500
Outstanding principal balance			632,500		632,500
Unamortized debt issuance costs			$ 15,100		$ 15,100
Maturity date					Apr. 30, 2026
Interest rate			0.00%	0.00%	0.00%	0.00%
Effective interest rate			0.50%		0.50%
Conversion price per share (in dollars per share)			$ 57.84		$ 57.84
Effective conversion price per share with call spread (in dollars per share)			$ 76.39		$ 76.39
Total shares of common stock subject to conversion (in shares)			10.9		10.9
Percentage of principal amount used as purchase price upon occurrence of fundamental change					100.00%
0.125% Notes [Member]
Convertible Debt [Abstract]
Outstanding principal balance			$ 548,800		$ 548,800
Unamortized debt issuance costs			$ 7,600		$ 7,600
Maturity date					Dec. 31, 2024
Interest rate			0.125%	0.125%	0.125%	0.125%	0.125%
Effective interest rate			0.50%		0.50%
Conversion price per share (in dollars per share)			$ 83.28		$ 83.28
Effective conversion price per share with call spread (in dollars per share)			$ 123.38		$ 123.38
Total shares of common stock subject to conversion (in shares)			6.6		6.6
Percentage of principal amount used as purchase price upon occurrence of fundamental change					100.00%
1% Notes [Member]
Convertible Debt [Abstract]
Principal amount repurchased	247,900		$ 247,900		$ 247,900
Repurchase of convertible notes	257,000
Outstanding principal balance			62,000		62,000
Unamortized debt issuance costs			$ 100		$ 100
Maturity date					Nov. 30, 2021
Interest rate			1.00%	1.00%	1.00%	1.00%	1.00%
Effective interest rate			1.40%		1.40%
Conversion price per share (in dollars per share)			$ 66.81		$ 66.81
Total shares of common stock subject to conversion (in shares)			0.9		0.9
Loss on early retirement of debt	$ 8,600
Percentage of principal amount used as purchase price upon occurrence of fundamental change					100.00%