Compensation Plans - Stock Options (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Options Outstanding
Beginning Balance	157,201	217,873	469,289
Granted	0	0	0
Exercised	(104,175)	(50,671)	(137,864)
Cancelled	0	0	(55)
Expired	(22,413)	(10,001)	(113,497)
Ending Balance	30,613	157,201	217,873	469,289
Options exercisable at period end	30,613	157,201	217,873
Weighted Average Exercise Price (in dollars per share)
Beginning Balance	$ 50.35	$ 46.66	$ 44.83
Granted	0.00	0.00	0.00
Exercised	43.75	36.62	39.55
Cancelled	0.00	0.00	39.62
Expired	59.83	39.62	47.72
Ending Balance	65.86	50.35	46.66	$ 44.83
Options exercisable at period end	$ 65.86	$ 50.35	$ 46.66
Weighted Average Remaining Contractual Term (in Years)
Weighted Average Remaining Contractual Term (in Years)	4 months	1 year 7 months 6 days	2 years	2 years
Options exercisable at period end	4 months	1 year 7 months 6 days	2 years
Aggregate Intrinsic Value
Aggregate Intrinsic Value of Stock Options	$ 203,291	$ 0	$ 3,066,839	$ 288,318
Options exercisable at end of period	$ 203,291	$ 0	$ 3,066,839