Earnings Per Common Share And Share Awards Summary Of Share-Based Award Transactions (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
StockOptionsAndStockAppreciationRightsSARS [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, Outstanding Beginning Balance	24,500	22,000
Number Of Shares, Outstanding Ending Balance	22,000	24,500	22,000
Number Of Shares, Exercisable as of March 31, 2017	22,000
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
Weighted Average Exercise Price, Outstanding Ending Balance	69.55	$ 65.85	$ 57.04
Weighted Average Exercise Price, Exercisable as of March 31, 2017	$ 69.55
Average Remaining Contractual Term, Outstanding Beginning Balance	4 years	3 years 10 months 6 days	3 years 11 months 4 days
Average Remaining Contractual Term, Outstanding Ending Balance	4 years	3 years 10 months 6 days	3 years 11 months 4 days
Average Remaining Contractual Term, Exercisable as of March 31, 2017	4 years
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 836,640	$ 945,055
Aggregate Intrinsic Value, Outstanding Ending Balance	1,949,215	$ 836,640	$ 945,055
Aggregate Intrinsic Value, Exercisable as of March 31, 2017	$ 1,949,215
SARs
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number Of Shares, SARs granted	0	4,500
Number Of Shares, Options exercised	(2,500)	(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	$ 0.00	$ 93.87
Weighted Average Exercise Price, Options exercised	$ 33.31	$ 32.00