Stock-Based Compensation - Stock Options Activity (Details) - Stock options $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Stock Options
Options outstanding at the beginning of the period (in shares) | shares	489
Exercised (in shares) | shares	(30)
Cancelled (in shares) | shares	(53)
Options outstanding at the end of the period (in shares) | shares	406
Options exercisable at the end of the period (in shares) | shares	406
Weighted Average Exercise Price Per Share
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 12.28
Exercised (in dollars per share) | $ / shares	8.79
Cancelled (in dollars per share) | $ / shares	13.96
Options outstanding at end of period, (in dollars per share) | $ / shares	12.31
Options exercisable at the end of period (in dollars per share) | $ / shares	$ 12.31
Weighted Average Remaining Life
Outstanding at the end of the period	9 months 18 days
Exercisable at the end of the period	9 months 18 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars) | $	$ 1,305
Exercisable at the end of the period (in dollars) | $	$ 1,305