Earnings (Loss) Per Share - Computation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Earnings Per Share [Abstract]
Net income (loss)	$ 5,325	$ 3,300	$ 2,544	$ 1,035	$ 14,824	$ 409	$ (2,846)	$ (4,890)	$ 12,204	$ 7,497	$ (7,699)
Denominator:
Denominator for basic earnings (loss) per share – weighted-average shares (in shares)	8,268	8,223	8,205	8,035	8,027	8,027	8,028	7,998	8,194	8,029	8,550
Effect of dilutive securities:
Employee restricted stock (in shares)									24	27	0
Denominator for diluted earnings (loss) per share – adjusted weighted-average shares and assumed conversions (in shares)	8,288	8,240	8,227	8,040	8,036	8,039	8,028	7,998	8,218	8,056	8,550
Basic earnings (loss) per share (in usd per share)	$ 0.65	$ 0.40	$ 0.31	$ 0.13	$ 1.85	$ 0.05	$ (0.35)	$ (0.61)	$ 1.49	$ 0.93	$ (0.90)
Diluted earnings (loss) per share (in usd per share)	$ 0.65	$ 0.40	$ 0.31	$ 0.13	$ 1.84	$ 0.05	$ (0.35)	$ (0.61)	$ 1.49	$ 0.93	$ (0.90)
Weighted-average anti-dilutive employee restricted stock (in shares)									77	1	11