Long-Term Obligations and Commitments, Convertible Notes (Details) $ / shares in Units, $ in Thousands, shares in Millions		1 Months Ended	12 Months Ended
		Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($) shares $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)	Nov. 30, 2014 USD ($)
Convertible Notes [Abstract]
Cost of call spread		$ 52,600
Purchase of note hedges		108,700	$ 0	$ 108,684	$ 0
Proceeds from issuance of warrants		$ 56,100	0	$ 56,110	0
Conversion price per share, including note hedges (in dollars per share) | $ / shares		$ 123.38		$ 123.38
Current debt		$ 0	293,161	$ 0
Loss on early retirement of debt			0	(21,865)	0
Amortization of debt discount and debt issuance costs			$ 38,700	$ 39,300	$ 35,200
0.125% Convertible Senior Notes [Member]
Convertible Notes [Abstract]
Maturity date			Dec. 15, 2024
Interest rate		0.125%	0.125%	0.125%
Conversion price per share (in dollars per share) | $ / shares			$ 83.28
Total shares of common stock subject to conversion (in shares) | shares			6.6
Percentage of principal amount used as purchase price upon occurrence of fundamental change			100.00%
Principal amount of convertible notes outstanding		$ 548,800	$ 548,800	$ 548,800
Unamortized portion of debt discount		105,200	86,000	105,200
Long-term debt		434,711	455,719	434,711
Carrying value of equity component		105,800	$ 105,800	105,800
Effective interest rate			4.90%
Amortization period of debt discount			5 years
0.125% Convertible Senior Notes [Member] | Level 2 [Member]
Convertible Notes [Abstract]
Fair value of outstanding notes		558,700	$ 564,900	558,700
0.125% Convertible Senior Notes [Member] | Borrowing Rate [Member]
Convertible Notes [Abstract]
Nonconvertible debt measurement input rate			0.044
0.125 Percent Convertible Senior Notes Issued in Exchange for 1 Percent Notes [Member]
Convertible Notes [Abstract]
Face amount of offering		439,300		439,300
0.125 Percent Convertible Senior Notes Issued under Subscription Agreements [Member]
Convertible Notes [Abstract]
Face amount of offering		109,500		109,500
1% Convertible Senior Notes [Member]
Convertible Notes [Abstract]
Principal amount repurchased		$ 375,600		$ 375,600
Face amount of offering						$ 185,500	$ 500,000
Maturity date			Nov. 30, 2021
Interest rate		1.00%	1.00%	1.00%
Conversion price per share (in dollars per share) | $ / shares			$ 66.81
Total shares of common stock subject to conversion (in shares) | shares			4.6
Percentage of principal amount used as purchase price upon occurrence of fundamental change			100.00%
Principal amount of convertible notes outstanding		$ 309,900	$ 309,900	$ 309,900
Unamortized portion of debt discount		32,800	15,800	32,800
Current debt			293,200
Long-term debt		275,333	0	275,333
Carrying value of equity component		33,500	$ 33,500	33,500
Loss on early retirement of debt		(21,900)
Effective interest rate	[1]		7.50%
Amortization period of debt discount			7 years
1% Convertible Senior Notes [Member] | Level 2 [Member]
Convertible Notes [Abstract]
Fair value of outstanding notes		$ 354,800	$ 338,500	$ 354,800
1% Convertible Senior Notes [Member] | Borrowing Rate [Member]
Convertible Notes [Abstract]
Nonconvertible debt measurement input rate			0.074
2 3/4 Percent Convertible Senior Notes [Member]
Convertible Notes [Abstract]
Principal amount repurchased						$ 61,100	$ 140,000
Interest rate			2.75%

[1] For our 1% Notes, our effective interest rate represents our effective interest rate after our December 2019 debt exchange.