Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Beginning stock options outstanding (in shares)	1,911,121	2,349,446	2,149,900
Granted (in shares)	374,215	425,204	587,862
Exercised (in shares)	(488,303)	(229,551)	(13,850)
Forfeited (in shares)	(132,252)	(633,978)	(374,466)
Ending stock options outstanding (in shares)	1,664,781	1,911,121	2,349,446
Weighted Average Exercise Price Per Share
Beginning stock options outstanding (in dollars per share)	$ 7.79	$ 8.39	$ 9.56
Granted (in dollars per share)	7.49	7.22	4.98
Exercised (in dollars per share)	5.76	5.75	4.86
Forfeited (in dollars per share)	7.89	10.36	9.89
Ending stock options outstanding (in dollars per share)	$ 8.31	$ 7.79	$ 8.39
Vested and expected to vest at December 31, 2017
Number of Shares	1,779,990
Weighted Average Exercise Price Per Share (in dollars per share)	$ 8.15
Weighted Average Contractual Life	5 years 9 months 29 days
Aggregate Intrinsic Value	$ 15
December 31, 2018
Number of Shares	1,247,450
Weighted Average Exercise Price Per Share (in dollars per share)	$ 8.56
Weighted Average Contractual Life	4 years 6 months 4 days
Aggregate Intrinsic Value	$ 14