Earnings Per Common Share - Computation of basic and diluted earnings per common share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic Earnings Per Share:
Net income available to common shareholders	$ 26,357	$ 40,996
Less: income allocated to participating securities	35	43
Net income allocated to common shareholders	$ 26,322	$ 40,953
Weighted average common shares outstanding including participating securities	36,026	37,332
Less: Participating securities	48	39
Average common shares	35,978	37,293
Basic earnings per common share	$ 0.73	$ 1.10
Diluted Earnings Per Share:
Net income allocated to common shareholders	$ 26,322	$ 40,953
Weighted average common shares outstanding for basic earnings per common share	35,978	37,293
Add: Dilutive effects of stock options and restricted stock units	112	64
Average shares and dilutive potential common shares	36,090	37,357
Diluted earnings per common share	$ 0.73	$ 1.10