Consolidated balance sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.000001	$ 0.000001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	23,472,430	23,423,150
Common stock, shares outstanding	23,472,430	23,423,150
Preferred stock, par value	$ 0.000001	$ 0.000001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0