17. Earnings per share (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 4,403,239	$ 15,758,756
Basic and diluted income per share	$ 0.42	$ 1.51
Basic and Diluted
Weighted average number of shares of common stock outstanding and potential dilutive shares of common stock	10,451,832	10,441,464