Condensed consolidated balance sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
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	23,492,161	23,472,430
Common stock, shares outstanding	23,492,161	23,472,430