Stock Option Plans - Summary of Option Activity (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Number of Shares
Outstanding at beginning of period (in shares) | shares	1,114,169
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Expired/Forfeited (in shares) | shares	(7,500)
Outstanding at end of period (in shares) | shares	1,106,669
Exercisable at end of period (in shares) | shares	593,419
Weighted Average Exercise Price per share
Outstanding at beginning of period (in usd per share) | $ / shares	$ 52.40
Granted (in usd per share) | $ / shares	0.00
Exercised (in usd per share) | $ / shares	0.00
Expired/Forfeited (in usd per share) | $ / shares	56.07
Outstanding at end of period (in usd per share) | $ / shares	52.38
Exercisable at end of period (in usd per share) | $ / shares	$ 50.86
Aggregate Intrinsic Value
Outstanding at beginning of period | $	$ 543,662
Granted | $	0
Exercised | $	0
Expired/Forfeited | $
Outstanding at end of period | $	2,056,820
Exercisable at end of period | $	$ 1,627,519