CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Stockholders' deficiency:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	100,000,000	58,500,000
Common stock, outstanding shares	12,354,014	0
Convertible preferred stock
Convertible Preferred Stock
Convertible preferred stock, authorized shares	0	42,500,000
Series A Redeemable Convertible Preferred Stock
Convertible Preferred Stock
Convertible preferred stock, authorized shares	0	9,000,000
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, issued shares	0	9,000,000
Convertible preferred stock, outstanding shares	0	9,000,000
Convertible preferred stock, liquidation preference	$ 0	$ 11,800
Series B Convertible Preferred Stock
Convertible Preferred Stock
Convertible preferred stock, authorized shares	0	21,500,000
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, issued shares	0	21,500,000
Convertible preferred stock, outstanding shares	0	21,500,000
Convertible preferred stock, liquidation preference	$ 0	$ 28,189
Series C Convertible Preferred Stock
Convertible Preferred Stock
Convertible preferred stock, authorized shares	0	12,000,000
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, issued shares	0	11,781,984
Convertible preferred stock, outstanding shares	0	11,781,984
Convertible preferred stock, liquidation preference	$ 0	$ 30,542