Earnings Per Common Share and Share Awards Summary Of Share-Based Award Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, Options exercised			(1,500)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Options exercised			$ 36.79
StockOptionsAndStockAppreciationRightsSARS
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, Outstanding Beginning Balance	24,500	22,000	21,000
Number Of Shares, Outstanding Ending Balance	25,000	24,500	22,000	21,000
Number Of Shares, Exercisable as of December 31, 2017	23,875
Number Of Shares, Unvested as of December 31, 2017	1,125
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 65.85	$ 57.04	$ 51.30
Weighted Average Exercise Price, Outstanding Ending Balance	93.40	$ 65.85	$ 57.04	$ 51.30
Weighted Average Exercise Price, Exercisable as of December 31, 2017	88.72
Weighted Average Exercise Price, Unvested as of December 31, 2017	$ 192.71
Average Remaining Contractual Term, Outstanding Beginning Balance	3 years 11 months 23 days	3 years 10 months 6 days	3 years 11 months 4 days	3 years 7 months 20 days
Average Remaining Contractual Term, Exercisable as of December 31, 2017	3 years 10 months 13 days
Average Remaining Contractual Term, Unvested as of December 31, 2017	6 years 4 months 17 days
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 836,640	$ 945,055	$ 453,510
Aggregate Intrinsic Value, Outstanding Ending Balance	2,623,720	$ 836,640	$ 945,055	$ 453,510
Aggregate Intrinsic Value, Exercisable as of December 31, 2017	2,617,375
Aggregate Intrinsic Value, Unvested as of December 31, 2017	$ 6,345
SARs
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, SARs granted	4,500	4,500	4,500
Number Of Shares, Options exercised	(4,000)	(2,000)	(2,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, SARs granted	$ 192.71	$ 93.87	$ 73.00
Weighted Average Exercise Price, Options exercised	$ 36.38	$ 32.00	$ 47.88