Significant Accounting Policies - Stock Transactions - Stock Option Plans (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Shares
Options Outstanding, beginning shares	552,759
Options granted, shares	47,100	97,900
Options exercised, shares	(17,064)	0
Options forfeited, shares	0
Options expired, shares	(607)
Options Outstanding, ending shares	582,188
Shares Exercisable	410,995
Weighted average exercise price
Weighted average exercise price, Options Outstanding, beginning (in dollars per share)	$ 7.26
Weighted average exercise price, Options granted (in dollars per share)	16.37	$ 10.06
Weighted average exercise price, Options exercised (in dollars per share)	7.91
Weighted average exercise price, Options forfeited (in dollars per share)	0.00
Weighted average exercise price, Options expired (in dollars per share)	11.48
Weighted average exercise price, Options Outstanding, ending (in dollars per share)	7.98
Weighted average exercise price, Options Exercisable (in dollars per share)	$ 6.14
Weighted average remaining contractual life , Options Outstanding	5 years 10 months 24 days		5 years 8 months 12 days
Weighted average remaining contractual life, Options exercisable	4 years 6 months
Aggregate intrinsic value: Options Outstanding	$ 5,224,156			$ 4,663,432
Aggregate intrinsic value, Options exercisable	$ 4,442,273