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, 2019 USD ($) shares $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2016 USD ($)	Nov. 30, 2014 USD ($)
Convertible Notes [Abstract]
Cost of call spread		$ 52,600
Purchase of note hedges		108,700	$ 108,684	$ 0	$ 0
Proceeds from issuance of warrants		$ 56,100	$ 56,110	0	0
Conversion price per share, including note hedges (in dollars per share) | $ / shares		$ 123.38	$ 123.38
Loss on early retirement of debt			$ (21,865)	0	0
Amortization of debt discount and debt issuance costs			$ 39,300	$ 35,200	$ 32,500
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	$ 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
Unamortized portion of debt discount		105,200	105,200
Long-term debt		434,711	434,711	$ 0
Carrying value of equity component		$ 105,800	$ 105,800
Effective interest rate		4.90%	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	$ 558,700
0.125% Convertible Senior Notes [Member] | Borrowing Rate [Member]
Convertible Notes [Abstract]
Nonconvertible debt measurement input rate		0.044	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%		1.00%	1.00%
Conversion price per share (in dollars per share) | $ / shares		$ 66.81	$ 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	$ 685,500
Unamortized portion of debt discount		32,800	32,800	110,800
Long-term debt		275,333	275,333	568,215
Carrying value of equity component		33,500	$ 33,500	219,000
Loss on early retirement of debt		$ 21,900
Effective interest rate	[1]	7.50%	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	$ 354,800	$ 725,000
1% Convertible Senior Notes [Member] | Borrowing Rate [Member]
Convertible Notes [Abstract]
Nonconvertible debt measurement input rate		0.074	0.074
2 3/4 Percent Convertible Senior Notes [Member]
Convertible Notes [Abstract]
Principal amount repurchased								$ 61,100	$ 140,000
Interest rate		2.75%	2.75%

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