Stock Based Compensation - Schedule of information with respect to stock options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Outstanding at December 31, 2017 (in shares)	761
Options granted (in shares)	101
Options exercised (in shares)	(168)
Forfeited and cancelled (in shares)	(16)
Expired (in shares)	0
Outstanding at December 31, 2018 (in shares)	678	761
Vested and expected to vest (in shares)	674
Total shares exercisable (in shares)	497
Shares remaining available for grant (in shares)	583
Weighted Average Exercise Price
Outstanding at December 31, 2017 (in dollars per share)	$ 5.80
Options granted (in dollars per share)	19.36
Options Exercised (in dollars per share)	5.19
Forfeited and cancelled (in dollars per share)	13.93
Expired (in dollars per share)	0.00
Outstanding at December 31, 2018 (in dollars per share)	7.89	$ 5.80
Vested and expected to vest (in dollars per share)	7.71
Total shares exercisable (in dollars per share)	$ 5.62
Aggregate Intrinsic Value
Outstanding		$ 2,748
Vested and expected to vest
Total shares exercisable