Earnings Per Common Share And Share Awards (Summary Of Share-Based Award Transactions) (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Common Share And Share Awards [Abstract]
Number Of Shares, Outstanding Beginning Balance	101,600	110,800
Number Of Shares, SARs granted	3,000	3,000
Number Of Shares, Options exercised	(6,130)	(7,700)
Number Of Shares, Options/SARs cancelled/forfeited/expired	(70)	(4,500)
Number Of Shares, Outstanding Ending Balance	98,400	101,600	110,800
Number Of Shares, Exercisable as of June 30, 2012	95,600
Number Of Shares, Unvested as of June 30, 2012	2,800
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 29.81	$ 28.77
Weighted Average Exercise Price, SARs granted	$ 50.50	$ 41.50
Weighted Average Exercise Price, Options exercised	$ 24.93	$ 20.15
Weighted Average Exercise Price, Options/SARs cancelled/forfeited/expired	$ 31.00	$ 28.61
Weighted Average Exercise Price, Outstanding Ending Balance	$ 30.74	$ 29.81	$ 28.77
Weighted Average Exercise Price, Exercisable as of June 30, 2012	$ 30.28
Weighted Average Exercise Price, Unvested as of June 30, 2012	$ 46.69
Average Remaining Contractual Term, Outstanding Beginning Balance	3 years 8 months 1 day	3 years 10 months 28 days	4 years 6 months 4 days
Average Remaining Contractual Term, Outstanding Ending Balance	3 years 8 months 1 day	3 years 10 months 28 days	4 years 6 months 4 days
Average Remaining Contractual Term, Exercisable as of June 30, 2012	3 years 7 months 10 days
Average Remaining Contractual Term, Unvested as of June 30, 2012	5 years 11 months 9 days
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 697,780	$ 353,955
Aggregate Intrinsic Value, Outstanding Ending Balance	2,576,857	697,780	353,955
Aggregate Intrinsic Value, Exercisable as of June 30, 2012	2,548,172
Aggregate Intrinsic Value, Unvested as of June 30, 2012	$ 28,685