Net loss per common stock (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Basic and Diluted Net Loss Per Share

The following have been excluded from the computation of basic and diluted net loss per common stock as their effect would have been antidilutive:

	DECEMBER 31, 2017		DECEMBER 31, 2016		DECEMBER 31, 2015
Outstanding stock options		2,069,167		1,378,352		865,457
Common stock warrants		—		—		11,363
Total		2,069,167		1,378,352		876,820