Summary Of Major Accounting Policies - Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic earnings per share:
Net income per consolidated statements of income	$ 289,017	$ 235,658	$ 200,531
Income allocable to paticipating securities	0	0	(709)
Net Income (Loss) Available to Common Stockholders, Basic	289,017	235,658	199,822
Basic shares outstanding	108,015	108,308	109,119
Basic earnings per share	$ 2.68	$ 2.18	$ 1.83
Diluted earnings per share:
Income allocable to participating securities	0	0	(706)
Earnings allocable to diluted common shareholders	$ 289,017	$ 235,658	$ 199,825
Diluted shares outstanding	108,617	109,001	109,535
Diluted earnings per share	$ 2.66	$ 2.16	$ 1.82