Stock-Based Compensation - Options Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) shares
Additional disclosures
Intrinsic value of options exercised (in dollars) | $	$ 11,665	$ 832
Proceeds from stock options exercised (in dollars) | $	$ 194	$ 0
Shares delivered as payment for exercise	362,440	7,930
Stock options exercised in cashless transaction	956,327	71,150
Gross cashless exercise value | $	$ 3,187	$ 104
2016 Plan
Number of shares
Outstanding at beginning of period (in shares)	3,059,690
Granted (in shares)	1,044,556
Exercised (in shares)	(1,054,764)
Forfeited (in shares)	(49,629)
Outstanding at end of the period (in shares)	2,999,853
Options vested and expected to vest at end of the period (in shares)	2,999,853
Exercisable at end of period (in shares)	1,393,742
Weighted average exercise price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 5.14
Granted (in dollars per share) | $ / shares	14.43
Exercised (in dollars per share) | $ / shares	3.21
Forfeited (in dollars per share) | $ / shares	10.52
Outstanding at end of period (in dollars per share) | $ / shares	8.97
Options vested and expected to vest at end of period (in dollars per share) | $ / shares	8.97
Exercisable at end of period (in dollars per share) | $ / shares	$ 3.37
Weighted average remaining contractual term
Outstanding	7 years 3 months 18 days
Options vested and expected to vest at of the period	7 years 3 months 18 days
Exercisable	5 years 3 months 18 days
Aggregate intrinsic value
Outstanding (in dollars) | $	$ 53,340
Options vested and expected to vest at end of period (in dollars) | $	53,340
Exercisable (in dollars) | $	32,572
Stock options | 2016 Plan
Additional disclosures
Total unrecognized compensation cost (in dollars) | $	$ 10,022
Weighted average period expected to be recognized	2 years 10 months 24 days
Non-employee options | 2016 Plan
Number of shares
Outstanding at end of the period (in shares)	150,212
Additional disclosures
Unvested options (in shares)	345