Benefit Plans (Summary Of Non-Qualified Stock Option Activity) (Details) (Non-Qualified Stock Options [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Non-Qualified Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, January 1, shares (in shares)	63,889	163,680	384,331
Outstanding, January 1, weighted average exercise price (in dollars per share)	$ 24.21	$ 24.51	$ 27.02
Exercised, shares (in shares)	(38,711)	(99,791)	(191,433)
Exercised, weighted average exercise price (in dollars per share)	$ 24.41	$ 24.71	$ 28.93
Expired, shares (in shares)	0	0	(29,218)
Expired, weighted average exercise price (in dollars per share)	$ 0.00	$ 0.00	$ 28.59
Outstanding and exercisable, December 31, shares (in shares)	25,178	63,889	163,680
Outstanding and exercisable, December 31, weighted average exercise price (in dollars per share)	$ 23.89	$ 24.21	$ 24.51