Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 74,023	$ 26,067	$ 211,171	$ 61,357
Net Income - diluted	$ 74,023	$ 26,067	$ 211,171	$ 61,357
Net income per common share - basic (in dollars per share)	$ 1.55	$ 0.55	$ 4.43	$ 1.29
Net income per common share - diluted (in dollars per share)	$ 1.54	$ 0.55	$ 4.40	$ 1.29
Weighted average common shares outstanding - basic (in shares)	47,737	47,476	47,666	47,406
Plus dilutive effect of potential common shares (in shares)	343	200	356	241
Weighted average common shares outstanding - diluted (in shares)	48,080	47,676	48,022	47,647
Common stock excluded from calculation of EPS (in shares)	21	84	26	79