Stock-Based Compensation (Summary Of Restricted Stock Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock-Based Compensation [Abstract]
Unvested, Shares, beginning balance	2,684,250	2,506,575	1,367,775
Granted, Shares	272,000	582,400	1,713,000
Vested, Shares	(384,125)	(381,025)	(548,250)
Forfeited, Shares	(29,136)	(23,700)	(25,950)
Unvested, Shares, ending balance	2,542,989	2,684,250	2,506,575
Unvested, Weighted-Average Grant Date Fair Value Per Share, beginning balance	$ 21.79	$ 21.53	$ 22.48
Granted, Weighted-Average Grant Date Fair Value Per Share	$ 23.40	$ 23.76	$ 20.37
Vested, Weighted-Average Grant Date Fair Value Per Share	$ 23.54	$ 22.92	$ 20.11
Forfeited, Weighted-Average Grant Date Fair Value Per Share	$ 24.19	$ 24.67	$ 25.07
Unvested, Weighted-Average Grant Date Fair Value Per Share, ending balance	$ 21.67	$ 21.79	$ 21.53