Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ 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
Net Income Per Common Share
Number of outstanding units not included in computation of Diluted EPS (in shares)							230,000	200,000
Warrants to purchase shares	78,000						78,000
Warrants exercise price	$ 57.47						$ 57.47
Numerator:
Net income	$ 9,684	$ 61,994	$ 35,900	$ 33,662	$ (25,715)	$ 29,988	$ 107,578	$ 37,935
Denominator:
Basic earnings per share weighted average shares	50,380,000			50,181,000			50,337,000	50,199,000
Dilution due to stock options and restricted stock units	345,000			441,000			389,000	246,000
Diluted earnings per share weighted average shares	50,725,000			50,622,000			50,726,000	50,445,000
Basic earnings per share (in dollars per share)	$ 0.19			$ 0.67			$ 2.14	$ 0.76
Diluted earnings per share (in dollars per share)	$ 0.19			$ 0.66			$ 2.12	$ 0.75