Stock-Based Compensation (Summary Of Changes In The Status Of Restricted Stock) (Details) (Restricted Stock Units [Member], USD $)	12 Months Ended
	Dec. 31, 2011
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested at 12/31/10, shares	66,359
Weighted average grant date non-vested at 12/31/10	$ 41.334
Granted, shares	22,620
Weighted average date granted	$ 50.720
Vested, shares	(21,403)
Weighted average grant date vested	$ 39.705
Forfeited, shares	(2,156)
Weighted average grant date forfeited	$ 43.276
Non-vested at 12/31/11, shares	65,420
Weighted average grant date non-vested at 12/31/11	$ 45.049