Stock-based compensation - Summary of stock option activity (Details)	10 Months Ended	12 Months Ended
	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Shares
Shares outstanding, beginning balance | shares		926,832
Shares granted | shares	1,020,234	994,748
Shares exercised | shares	(13,572)	(47,280)
Shares canceled or forfeited | shares		(49,327)
Shares outstanding, ending balance | shares	926,832	1,824,973
Shares exercisable | shares		372,508
Shares vested or expected to vest | shares		1,617,617
Weighted-Average Exercise Price
Shares outstanding, beginning balance, weighted average exercise price (in usd per share) | $ / shares		$ 3.40
Shares granted, weighted average exercise price (in usd per share) | $ / shares		13.07
Shares exercised, weighted average exercise price (in usd per share) | $ / shares	$ 0.60	8.63
Shares canceled or forfeited, weighted average exercise price (in usd per share) | $ / shares		10.69
Shares outstanding, ending balance, weighted average exercise price (in usd per share) | $ / shares	$ 3.40	8.34
Shares exercisable, weighted average exercise price (in usd per share) | $ / shares		5.17
Shares vested or expected to vest, weighted average exercise price (in usd per share) | $ / shares		$ 8.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, weighted average remaining contractual term	9 years 8 months 1 day	8 years 10 months 24 days
Exercisable, weighted average remaining contractual term		8 years 9 months
Vested or expected to vest, weighted average remaining contractual term		8 years 9 months 26 days
Outstanding, aggregate intrinsic value | $	$ 6,846,054	$ 9,073,673
Exercisable, aggregate intrinsic value | $		2,883,387
Vested or expected to vest, aggregate intrinsic value | $		$ 8,625,871