Earnings Per Share (Comparison of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share
Basic earnings per share	$ 2.45	$ 3.66	$ 2.69	$ 6.34
Net income	$ 93,800	$ 183,959	$ 102,420	$ 317,699
Weighted average common shares outstanding	38,346,489	50,222,974	38,061,724	50,123,945
Warrants and options	333,837	1,486,465	503,529	1,534,861
Restricted stock units	507,969	456,946	503,954	469,301
LTIP awards	612,458	808,025	804,211	958,601
Weighted average common shares and common share equivalents outstanding - diluted	39,800,753	52,974,410	39,873,418	53,086,708
Diluted earnings per share	$ 2.36	$ 3.47	$ 2.57	$ 5.98