Benefit Plans (Summary Of Restricted Stock Activity) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Time-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares/units, Jan. 1	35,800	70,033
Granted, Shares		5,000
Vested, Shares	(32,466)	(33,516)
Nonvested shares/units, March 31	3,334	41,517
Nonvested shares, Jan. 1, Weighted Average Fair Value	$ 30.87	$ 32.27
Granted, Weighted Average Fair Value		$ 39.86
Vested, Weighted Average Fair Value	$ 29.95	$ 35.34
Nonvested shares, March 31, Weighted Average Fair Value	$ 39.86	$ 30.71
Performance-Contingent Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares/units, Jan. 1	301,738	296,190
Granted, Shares	45,612	64,217
Vested, Shares	(65,172)	(53,274)
Forfeited, Shares	(70,527)	(5,395)
Nonvested shares/units, March 31	211,651	301,738
Nonvested shares, Jan. 1, Weighted Average Fair Value	$ 32.60	$ 32.32
Granted, Weighted Average Fair Value	$ 43.05	$ 38.75
Vested, Weighted Average Fair Value	$ 32.56	$ 37.93
Forfeited, Weighted Average Fair Value	$ 39.93	$ 38.00
Nonvested shares, March 31, Weighted Average Fair Value	$ 32.42	$ 32.60