Earnings Per Share (Computation Of Basic And Diluted Earnings (Loss) Per Share) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 84,945	$ 64,896	$ 189,248	$ 744,777
Weighted average number of common shares outstanding	214,068	212,480	213,831	212,356
Weighted average number of common shares and common stock equivalent shares outstanding	216,314	214,922	217,167	215,627
Basic income per common share	$ 0.40	$ 0.31	$ 0.89	$ 3.51
Diluted income per share	$ 0.39	$ 0.30	$ 0.87	$ 3.45
Stock Options [Member] | Earnings Per Share, Diluted [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of stock options	2,246	2,442	3,336	3,271
Restricted Stock [Member] | Earnings Per Share, Diluted [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of stock options	0		0
Earnings Per Share, Basic [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	84,945	64,896	189,248	744,777
Weighted average number of common shares outstanding	214,068	212,480	213,831	212,356
Basic income per common share	$ 0.40	$ 0.31	$ 0.89	$ 3.51
Earnings Per Share, Diluted [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 84,945	$ 64,896	$ 189,248	$ 744,777
Weighted average number of common shares outstanding	214,068	212,480	213,831	212,356
Weighted average number of common shares and common stock equivalent shares outstanding	216,314	214,922	217,167	215,627
Diluted income per share	$ 0.39	$ 0.30	$ 0.87	$ 3.45