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, 2017	Dec. 31, 2016
Number of Shares
Outstanding at December 31, 2016 (in shares)	949
Options granted (in shares)	149
Options exercised (in shares)	(271)
Forfeited and cancelled (in shares)	(31)
Expired (in shares)	(35)
Outstanding at 2017 (in shares)	761	949
Vested and expected to vest (in shares)	272
Total shares exercisable (in shares)	41
Shares remaining available for grant (in shares)	687
Weighted Average Exercise Price
Outstanding at December 31, 2016 (in dollars per share)	$ 5.22
Options granted (in dollars per share)	8.82
Options Exercised (in dollars per share)	9.06
Forfeited and cancelled (in dollars per share)	5.64
Expired (in dollars per share)	5.17
Total shares exercisable (in dollars per share)	5.80
Vested and expected to vest (in dollars per share)	7.30
Outstanding at 2017 (in dollars per share)	$ 5.46	$ 5.22
Aggregate Intrinsic Value
Outstanding	$ 2,748	$ 264
Vested and expected to vest	558
Total shares exercisable	$ 159