Earnings Per Share - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
BASIC
Net income (loss)	$ (955)	$ 5,593	$ 6,993	$ 6,168	$ 14,400	$ 5,846	$ 11,631	$ 26,414
Weighted-average common shares outstanding (in shares)	13,392			13,928			13,622	13,935
Basic earnings per share (in dollars per share)	$ (0.07)			$ 0.44			$ 0.85	$ 1.90
DILUTED
Net income (loss)	$ (955)	$ 5,593	$ 6,993	$ 6,168	$ 14,400	$ 5,846	$ 11,631	$ 26,414
Weighted-average common shares outstanding (in shares)	13,392			13,928			13,622	13,935
Dilutive effect of stock options, restricted stock and common stock warrants (in shares)	0			277			298	254
Weighted-average common shares outstanding on a diluted basis (in shares)	13,392			14,205			13,920	14,189
Diluted earnings per share (in dollars per share)	$ (0.07)			$ 0.43			$ 0.84	$ 1.86