Stockholders' Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net (loss) income	$ 189	$ (840)	$ (1,172)	$ 345	$ 21,384	$ 3,727	$ 1,498	$ 854	$ (1,479)	$ (15,306)	$ 13,979
Denominator:
Basic and diluted weighted average common shares outstanding (shares)									19,667,891	20,210,260	20,586,066
Basic and diluted net (loss) income per common share (usd per share)	$ 0.01	$ (0.04)	$ (0.06)	$ 0.02	$ (1.07)	$ 0.19	$ 0.07	$ 0.04	$ (0.08)	$ (0.76)	$ 0.68
Restricted stock units
Denominator:
Restricted stock units (shares)									178,279	90,665	0