Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Stock Option Activity and Outstanding Options
Options outstanding (in shares)	297
Forfeited, canceled or expired (in shares)	(4)
Exercised (in shares)	(127)
Options outstanding (in shares)	166	297
Stock Option Activity and Weighted-Average Exercise Price
Beginning of period, Weighted Average Exercise Price (in dollars per share)	$ 5.37
Forfeited, canceled or expired, Weighted Average Exercise Price (in dollars per share)	17.48
Exercises, Weighted Average Exercise Price (in dollars per share)	2.89
End of period, Weighted Average Exercise Price (in dollars per share)	$ 6.97	$ 5.37
Options outstanding, Number (in shares)	297	297		166
Options outstanding, Weighted Average Exercise Price (in dollars per share)	$ 5.37	$ 5.37		$ 6.97
Options outstanding, Aggregate Intrinsic Value				$ 698
Options outstanding, Weighted-Average Remaining Contractual Life	1 year 9 months 18 days
Options exercisable, Number of Options Exercisable				166
Options exercisable, Weighted-Average Exercise Price				$ 6.97
Options exercisable, aggregate intrinsic value				$ 698
Options exercisable, Weighted average remaining contractual term	1 year 9 months 18 days
Vested and expected to vest				166
Vested and expected to vest, Weighted Average Exercise Price				$ 6.97
Vested and expected to vest, Aggregate Intrinsic Value				$ 698
Vested and expected to vest, remaining contractual term (in years)	1 year 9 months 18 days
General and administrative	$ 1,981	$ 1,856	$ 2,613
Stock options
Stock Option Activity and Weighted-Average Exercise Price
General and administrative	$ 6	$ 84	$ 389
Compensation expense for unvested stock options				$ 3,700
Minimum | Stock options
Stock Option Activity and Weighted-Average Exercise Price
Weighted average period for unvested stock options	3 months 18 days
Maximum | Stock options
Stock Option Activity and Weighted-Average Exercise Price
Weighted average period for unvested stock options	1 year 6 months