Earnings Per Share (Net Income Per Share Basic And Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014
Numerator:
Income from continuing operations									$ 681,813	$ 575,667	$ 21,985
Loss from discontinued operations, net of income taxes									0	0	(42,704)
Net income (loss)	$ 207,113	$ 270,857	$ 93,495	$ 110,348	$ 165,718	$ 158,857	$ 106,833	$ 144,259	$ 681,813	$ 575,667	$ (20,719)
Denominator:
Denominator for basic earnings per share - weighted-average shares outstanding									130,853	136,030	150,779
Effect of dilutive employee stock awards									2,196	2,653	2,493
Effect of dilutive Convertible Notes									1,422	5,769	2,231
Effect of dilutive warrants									1,024	1,482	0
Denominator for diluted earnings per share - weighted-average shares outstanding									135,495	145,934	155,503
Basic earnings (loss) per share:
Income from continuing operations (USD per share)									$ 5.21	$ 4.23	$ 0.15
(Loss) income from discontinued operations (USD per share)									0	0	(0.28)
Basic net earnings (loss) per share (USD per share)	$ 1.59	$ 2.08	$ 0.71	$ 0.84	$ 1.24	$ 1.18	$ 0.79	$ 1.04	5.21	4.23	(0.13)
Diluted earnings (loss) per share:
Income from continuing operations (USD per share)									5.03	3.94	0.14
(Loss) income from discontinued operations (USD per share)									0	0	(0.27)
Diluted net earnings (loss) per share (USD per share)	1.56	$ 2.04	$ 0.70	$ 0.78	1.15	$ 1.08	$ 0.73	$ 0.99	5.03	3.94	$ (0.13)
Senior Notes Due 2019
Diluted earnings (loss) per share:
Strike price of warrants (in dollars per share)	$ 94.42				$ 94.94				$ 94.42	$ 94.94
Stated interest rate (percent)												0.50%