Earnings Per Common Share And Share Awards Summary Of Share-Based Award Transactions (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, Options exercised	(2,400)	(6,380)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Options exercised	$ 28.38	$ 25.17
StockOptionsAndStockAppreciationRightsSARS [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, Outstanding Beginning Balance	98,150	101,600
Number Of Shares, Options/SARs cancelled/forfeited/expired	0	(70)
Number Of Shares, Outstanding Ending Balance	19,250	98,150	101,600
Number Of Shares, Exercisable as of June 30, 2013	16,750
Number Of Shares, Unvested as of June 30. 2013	2,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 30.74	$ 29.81
Weighted Average Exercise Price, Options/SARs cancelled/forfeited/expired	$ 0.00	$ 31.00
Weighted Average Exercise Price, Outstanding Ending Balance	$ 45.55	$ 30.74	$ 29.81
Weighted Average Exercise Price, Exercisable as of June 30, 2013	$ 42.26
Weighted Average Exercise Price, Unvested as of June 30, 2013	$ 67.54
Average Remaining Contractual Term, Outstanding Beginning Balance	3 years 10 months 24 days	3 years 2 months 1 day	3 years 10 months 28 days
Average Remaining Contractual Term, Outstanding Ending Balance	3 years 10 months 24 days	3 years 2 months 1 day	3 years 10 months 28 days
Average Remaining Contractual Term, Exercisable as of June 30, 2013	3 years 6 months 16 days
Average Remaining Contractual Term, Unvested as of June 30, 2013	6 years 3 months 23 days
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 2,871,710	$ 697,780
Aggregate Intrinsic Value, Outstanding Ending Balance	490,770	2,871,710	697,780
Aggregate Intrinsic Value, Exercisable as of June 30, 2013	480,800
Aggregate Intrinsic Value, Unvested as of June 30, 2013	$ 9,970
SARs
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, SARs granted	3,000	3,000
Number Of Shares, Options exercised	(79,500)	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, SARs granted	$ 71.59	$ 50.50
Weighted Average Exercise Price, Options exercised	$ 28.77	$ 0.00