Earnings (Loss) Per Common Share (EPS) - Basic EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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, Basic and Diluted [Abstract]
Net income (loss)	$ 15,378	$ (3,009)	$ (19,058)	$ (3,154)	$ (4,205)	$ (3,398)	$ 6,859	$ 6,195	$ (9,843)	$ 5,451	$ 42,017
Average common shares outstanding (in shares)									55,434	55,075	52,268
Basic EPS (in dollars per share)	$ 0.28	$ (0.05)	$ (0.34)	$ (0.06)	$ (0.08)	$ (0.06)	$ 0.12	$ 0.11	$ (0.18)	$ 0.10	$ 0.80