Earnings per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Net income	$ 2,085	$ 16,468	$ 2,923	$ 32,547
Net income allocated to unvested restricted stock awards	(3)	(60)	0	(128)
Net income allocated to common shares	$ 2,082	$ 16,408	$ 2,923	$ 32,419
Weighted average shares outstanding	29,187	29,288	29,237	29,283
Average unvested restricted stock awards	(38)	(107)	(53)	(119)
Denominator for basic earnings per share—weighted-average shares outstanding	29,149	29,181	29,184	29,164
Effect of dilutive securities—employee stock options and restricted stock units	15	62	35	59
Denominator for diluted earnings per share—adjusted weighted-average shares outstanding	29,164	29,243	29,219	29,223
Basic earnings per share	$ 0.07	$ 0.56	$ 0.10	$ 1.11
Diluted earnings per share	$ 0.07	$ 0.56	$ 0.10	$ 1.11
Average antidilutive options and restricted stock units excluded from computation of diluted earnings per share	705	325	451	327