Share-Based Compensation (Schedule Of Share And Dividend Equivalent Share Award Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Share-Based Compensation [Abstract]
Number of share equivalents, Beginning Balance	119,194		67,361		34,497
Dividend equivalents, Beginning Balance	3,741		1,886		403
Total share equivalents, Beginning Balance	122,935		69,247		35,350
Value of share equivalents, Beginning Balance	$ 7,269,000	[1]	$ 3,726,000	[1]	$ 1,696,800	[1]
Number of share equivalents, Granted	131,099		58,124		32,414
Dividend equivalents, Granted	6,152		2,847		1,483
Total share equivalents, Granted	137,251		60,971		33,897
Value of share equivalents, Granted	6,766,000	[1]	3,605,000	[1]	1,824,000	[1]
Number of share equivalents, Forfeited share equivalents	(5,917)		(1,250)
Dividend equivalents, Forfeited share equivalents	(179)		(9)
Total share equivalents, Forfeited share equivalents	(6,096)		(1,259)
Value of share equivalents, Forfeited share equivalents	301,000	[1]	74,000	[1]
Number of share equivalents, Vested share equivalents	(11,455)		(5,041)
Dividend equivalents, Vested share equivalents	(772)		(983)
Total share equivalents, Vested share equivalents	(12,227)		(6,024)
Value of share equivalents, Vested share equivalents	622,000	[1]	356,000	[1]
Number of share equivalents, Ending Balance	232,921		119,194		67,361
Dividend equivalents, Ending Balance	8,942		3,741		1,886
Total share equivalents, Ending Balance	241,863		122,935		69,247
Value of share equivalents, Ending Balance	$ 11,924,000	[1]	$ 7,269,000	[1]	$ 3,726,000	[1]
Market price of Company stock	$ 49.30		$ 59.13		$ 53.81

[1] Except for vested share payments, which are based on the cash paid at the time of vesting, the value of share equivalents is calculated based on the market price of the Company's stock at the end of the respective periods. The market price of the Company's stock was $49.30, $59.13, and $53.81 on December 31, 2011, 2010, and 2009, respectively.