Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Apr. 15, 2019	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average warrant strike price (in USD per share)		$ 94.18		$ 94.52
Numerator:
Net income	$ 98,227	$ 270,857	$ 392,355	$ 474,700
Denominator:
Denominator for basic net earnings per share - weighted-average shares outstanding (shares)	123,255,000	130,277,000	123,835,000	131,020,000
Effect of dilutive employee stock awards (shares)	2,608,000	1,823,000	2,572,000	2,050,000
Effect of dilutive Convertible Notes (shares)	0	0	0	1,901,000
Effect of dilutive warrants (shares)	0	555,000	0	1,326,000
Denominator for net diluted earnings per share - weighted-average shares outstanding (shares)	125,863,000	132,655,000	126,407,000	136,297,000
Basic earnings per share (in dollars per share)	$ 0.80	$ 2.08	$ 3.17	$ 3.62
Diluted earnings per share (in dollars per share)	$ 0.78	$ 2.04	$ 3.10	$ 3.48
Senior Notes Due 2019 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate percentage					0.50%	0.50%