Common stock (Tables)

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Restricted common stock activity

The following is a summary of restricted common stock activity:

	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2015	2,202,262		$	0.10
Issued	—		—
Vested	(1,016,304	)	0.10
Forfeited	—		—
Non-vested at December 31, 2016	1,185,958		$	0.10

Shares reserved for future issuance

The Company has reserved the following number of shares of common stock for future issuance:

	As of December 31,
	2016	2015
Stock-based compensation awards	2,722,573	2,031,528
Vesting of restricted common stock	1,196,792	2,202,262
Employee stock purchase plan	354,569	175,131
Total	4,273,934	4,408,921