Benefit Plans (Summary Of Non-Qualified Stock Option Activity) (Details) (Non-Qualified Stock Options [Member], USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Non-Qualified Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Jan. 1, Shares	63,889	163,680
Exercised, Shares	(13,400)	(20,591)
Outstanding and exercisable, March 31, Shares	50,489	143,089
Outstanding, Jan. 1, Weighted Average Exercise Price	$ 24.21	$ 24.51
Exercised, Weighted Average Exercise Price	$ 24.83	$ 27.79
Outstanding and exercisable, March 31, Weighted Average Exercise Price	$ 24.04	$ 24.04