Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share, Basic [Abstract]
Net income	$ 176,972	$ 158,992
Weighted average common shares outstanding	33,181,729	34,613,606
Basic earnings per share	$ 5.33	$ 4.59
Earnings Per Share, Diluted [Abstract]
Net income	$ 176,972	$ 158,992
Weighted average common shares outstanding	33,181,729	34,613,606
Share equivalents:
Warrants and options	487,986	482,207
RSUs and LTIP awards	188,537	335,575
Employee share purchase plan	3,302	455
Weighted average common shares and common share equivalents outstanding - diluted	33,861,554	35,431,843
Diluted earnings per share	$ 5.23	$ 4.49