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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Numerator:
Income from continuing operations					$ (283,889)	$ 126,720	$ 108,829	$ 70,325	$ 575,667	$ 21,985	$ 469,855
(Loss) income from discontinued operations, net of income taxes					0	0	0	(42,704)	0	(42,704)	66,257
Net income (loss)	$ 165,718	$ 158,857	$ 106,833	$ 144,259	$ (283,889)	$ 126,720	$ 108,829	$ 27,621	$ 575,667	$ (20,719)	$ 536,112
Denominator:
Denominator for basic earnings per share - weighted-average shares outstanding									136,030	150,779	155,134
Effect of dilutive employee stock awards									2,653	2,493	1,950
Effect of dilutive Convertible Notes									5,769	2,231	0
Effect of dilutive warrants									1,482	0	0
Denominator for diluted earnings per share - weighted-average shares outstanding									145,934	155,503	157,084
Basic earnings (loss) per share:
Income from continuing operations (USD per share)					$ (1.93)	$ 0.84	$ 0.72	$ 0.46	$ 4.23	$ 0.15	$ 3.03
(Loss) income from discontinued operations (USD per share)									0.00	(0.28)	0.43
Basic net earnings (loss) per share (USD per share)	$ 1.24	$ 1.18	$ 0.79	$ 1.04	(1.93)	0.84	0.72	0.18	4.23	(0.13)	3.46
Diluted earnings (loss) per share:
Income from continuing operations (USD per share)					(1.93)	0.82	0.70	0.44	3.94	0.14	2.99
(Loss) income from discontinued operations (USD per share)									0.00	(0.27)	0.42
Diluted net earnings (loss) per share (USD per share)	1.15	$ 1.08	$ 0.73	$ 0.99	$ (1.93)	$ 0.82	$ 0.70	$ 0.17	3.94	$ (0.13)	$ 3.41
Senior Notes Due 2019
Diluted earnings (loss) per share:
Strike price of warrants (in dollars per share)	94.94								94.94
Stated interest rate (percent)												0.50%
Convertible debt, conversion price (in dollars per share)	$ 71.68								$ 71.68