Stock-based compensation - Schedule of Stock Options Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding, Number of Shares, beginning balance | shares	5,840,538
Options granted, Number of Shares | shares	711,700
Options exercised, Number of Shares | shares	(475,193)
Options forfeited, Number of Shares | shares	(463,708)
Options Outstanding, Number of Shares, ending balance | shares	5,613,337	5,840,538
Exercisable, Number of Shares, ending balance | shares	983,334
Options Outstanding, Weighted Average Exercise Price, beginning balance | $ / shares	$ 5.11
Options granted, Weighted Average Exercise Price | $ / shares	10.58
Options exercised, Weighted Average Exercise Price | $ / shares	7.79
Options forfeited, Weighted Average Exercise Price | $ / shares	15.83
Options Outstanding, Weighted Average Exercise Price, ending balance | $ / shares	4.69	$ 5.11
Options Exercisable, Weighted Average Exercise Price, ending balance | $ / shares	$ 7.66
Weighted average remaining contractual life, options outstanding	8 years 7 months 24 days	7 years 8 months 19 days
Weighted average remaining contractual life, options exercisable	5 years 9 months 3 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 66,953	$ 45,037
Exercisable, Aggregate Intrinsic Value | $	$ 8,861