Benefit Plans (Summary Of Restricted Stock Activity) (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Time-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	35,800	70,033
Nonvested shares, January 1, weighted average fair value (in dollars per share)	$ 30.87	$ 32.27
Granted (in shares)	0	5,000
Granted, weighted average fair value (in dollars per share)	$ 0.00	$ 39.86
Vested (in shares)	(32,466)	(38,633)
Vested, weighted average fair value (in dollars per share)	$ 29.95	$ 34.60
Forfeited (in shares)	0	(600)
Forfeited, weighted average fair value (in dollars per share)	$ 0.00	$ 29.41
Nonvested, September 30 (in shares/awards)	3,334	35,800
Nonvested shares, September 30, weighted average fair value (in dollars per share)	$ 39.86	$ 30.87
Performance-Contingent Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	301,738	296,190
Nonvested shares, January 1, weighted average fair value (in dollars per share)	$ 32.60	$ 32.32
Granted (in shares)	45,612	64,217
Granted, weighted average fair value (in dollars per share)	$ 43.05	$ 38.75
Vested (in shares)	(65,172)	(53,274)
Vested, weighted average fair value (in dollars per share)	$ 32.56	$ 37.93
Forfeited (in shares)	(70,527)	(5,395)
Forfeited, weighted average fair value (in dollars per share)	$ 39.93	$ 38.00
Nonvested, September 30 (in shares/awards)	211,651	301,738
Nonvested shares, September 30, weighted average fair value (in dollars per share)	$ 32.42	$ 32.60