Stock Based Compensation - Schedule of activity with respect to non-vested stock options (Details) - Non vested equity awards shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Shares
Balance at January 1, 2018 (in shares) | shares	158
Granted (in shares) | shares	79
Vested (in shares) | shares	(31)
Forfeited and cancelled (in shares) | shares	(13)
Balance at December 31, 2018 (in shares) | shares	193
Weighted Average grant- date fair value
Balance at January 1, 2018 (in dollars per share) | $ / shares	$ 6.49
Granted (in dollars per share) | $ / shares	17.08
Vested (in dollars per share) | $ / shares	10.81
Forfeited and cancelled (in dollars per share) | $ / shares	10.21
Balance at 2018 (in dollars per share) | $ / shares	$ 9.88