Earnings per share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ 1,340,892	$ (106,909)	$ 3,399,385	$ 237,585
Weighted average common shares outstanding	5,834,520	3,936,638	5,820,834	3,391,274
Effect of dilutive stock options (in shares)	261,813	307,215	271,201	307,548
Diluted shares	6,096,333	4,243,853	6,092,035	3,698,822
Basic earnings per common share (in dollars per share)	$ 0.23	$ (0.03)	$ 0.58	$ 0.07
Diluted earnings per common share (in dollars per share)	$ 0.22	$ (0.03)	$ 0.56	$ 0.06