Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Number Of Options
Outstanding at December 31, 2017 (in shares)	13,180,950
Options granted (in shares)	0
Options exercised (in shares)	(2,108,485)
Options forfeited (in shares)	(289,712)
Options forfeited or canceled (in shares)	(6,941)
Outstanding at June 30, 2018 (in shares)	10,775,812	13,180,950
Options exercisable at June 30, 2018 (in shares)	7,833,599
Weighted- Average Exercise Price
Outstanding at December 31, 2017 (in dollars per share)	$ 6.30
Options granted (in dollars per share)	0.00
Options exercised (in dollars per share)	5.10
Options forfeited (in dollars per share)	9.18
Options forfeited or canceled (in dollars per share)	8.44
Outstanding at June 30, 2018 (in dollars per share)	6.46	$ 6.30
Options exercisable at June 30, 2018 (in dollars per share)	$ 5.49
Stock Option Activity, Additional Disclosures
Weighted average remaining contractual life outstanding	6 years 6 months 25 days	7 years 7 days
Weighted average remaining contractual life exercisable	6 years 7 days
Options outstanding, Aggregate intrinsic value	$ 179,242	$ 329,786
Options exercised, Aggregate intrinsic value	0
Options exercisable, Aggregate intrinsic value	$ 137,856