Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Net income (loss)	$ (21,537)	$ 2,288	$ 1,587	$ 246	$ 2,001	$ 1,599	$ 1,996	$ (1,663)	$ (17,416)	$ 3,933	$ 18,343
Less: Net (income) loss attributable to participating securities									316	(38)	(373)
Net income (loss) attributable to common stockholders									$ (17,100)	$ 3,895	$ 17,970
Denominator
Weighted average shares outstanding used in basic per common share computations (in shares)									13,419	13,255	11,083
Basic EPS (in dollars per share)	$ (1.57)	$ 0.17	$ 0.11	$ 0.02	$ 0.15	$ 0.12	$ 0.15	$ (0.13)	$ (1.27)	$ 0.29	$ 1.62
Numerator
Net income (loss) attributable to common stockholders									$ (17,100)	$ 3,895	$ 17,970
Reallocation of net income (loss) attributable to participating securities									0	0	0
Net income (loss) attributable to common stockholders for diluted EPS									$ (17,100)	$ 3,895	$ 17,970
Denominator
Weighted average shares outstanding used in basic per common share computations (in shares)									13,419	13,255	11,083
Weighted average effect of dilutive securities:
Performance share awards (in shares)									0	0	0
Weighted average shares outstanding used in diluted per common share computations (in shares)									13,419	13,255	11,083
Diluted EPS (in dollars per share)	$ (1.57)	$ 0.17	$ 0.11	$ 0.02	$ 0.15	$ 0.12	$ 0.15	$ (0.13)	$ (1.27)	$ 0.29	$ 1.62