Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share
Total anti-dilutive shares (in shares)									3,831	0	17,894
Net income (loss)	$ 16,071	$ 6,815	$ 31,054	$ (15,748)	$ 18,750	$ 5,691	$ 10,035	$ (6,951)	$ 38,192	$ 27,525	$ (858)
Weighted average shares outstanding - basic	38,157,402	38,133,598	37,958,408	37,541,452	37,411,847	37,349,144	37,299,766	37,001,977	37,948,796	37,267,188	36,764,551
Effect of potentially dilutive restricted stock units and options									649,534	797,429
Weighted average shares outstanding - diluted	38,911,299	38,637,536	38,325,872	37,541,452	38,415,108	37,986,860	37,887,559	37,001,977	38,598,330	38,064,617	36,764,551
Basic and diluted:
Basic income (loss) per share	$ 0.42	$ 0.18	$ 0.82	$ (0.42)	$ 0.50	$ 0.15	$ 0.27	$ (0.19)	$ 1.01	$ 0.74	$ (0.02)
Diluted income (loss) per share	$ 0.41	$ 0.18	$ 0.81	$ (0.42)	$ 0.49	$ 0.15	$ 0.26	$ (0.19)	$ 0.99	$ 0.72	$ (0.02)
Unvested restricted stock units and unexercised options
Earnings Per Share
Total anti-dilutive shares (in shares)											709,309