Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Number Of Options
Outstanding at December 31, 2016 (in shares)	13,291,684
Options granted (in shares)	1,137,046
Options exercised (in shares)	(660,634)
Options forfeited or canceled (in shares)	(469,757)
Outstanding at September 30, 2017 (in shares)	13,298,339	13,291,684
Options exercisable at September 30, 2017 (in shares)	8,151,136
Weighted- Average Exercise Price
Outstanding at December 31, 2016 (in dollars per share)	$ 5.85
Options granted (in dollars per share)	10.78
Options exercised (in dollars per share)	3.81
Options forfeited or canceled (in dollars per share)	7.87
Outstanding at September 30, 2017 (in dollars per share)	6.30	$ 5.85
Options exercisable at September 30, 2017 (in dollars per share)	$ 4.69
Stock Option Activity, Additional Disclosures
Weighted average remaining contractual life outstanding	7 years 3 months 7 days	7 years 8 months 27 days
Weighted average remaining contractual life exercisable	6 years 4 months 2 days
Options outstanding, Aggregate intrinsic value	$ 249,825	$ 61,774
Options exercised, Aggregate intrinsic value	14,058
Options exercisable, Aggregate intrinsic value	$ 166,304