Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share
Net income (loss)	$ 18,750	$ 5,691	$ 10,035	$ (6,951)	$ 4,463	$ 4,369	$ 12,928	$ (22,618)	$ 27,525	$ (858)	$ (104,671)
Weighted average shares outstanding - basic	37,411,847	37,349,144	37,299,766	37,001,977	36,906,938	36,856,881	36,790,401	36,498,482	37,267,188	36,764,551	36,270,920
Effect of potentially dilutive restricted stock units and options									797,429
Weighted average shares outstanding - diluted	38,415,108	37,986,860	37,887,559	37,001,977	37,721,662	37,556,594	37,404,360	36,498,482	38,064,617	36,764,551	36,270,920
Total anti-dilutive shares (in shares)									0	17,894	473,037
Basic and diluted:
Basic (loss) earnings per share	$ 0.50	$ 0.15	$ 0.27	$ (0.19)	$ 0.12	$ 0.12	$ 0.35	$ (0.62)	$ 0.74	$ (0.02)	$ (2.89)
Diluted income (loss) per share	$ 0.49	$ 0.15	$ 0.26	$ (0.19)	$ 0.12	$ 0.12	$ 0.35	$ (0.62)	$ 0.72	$ (0.02)	$ (2.89)
Unvested restricted stock units and unexercised options
Earnings Per Share
Total anti-dilutive shares (in shares)										709,309	295,718