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								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic Earnings Per Share:
Net income available to common shareholders	$ 25,310	$ 28,360	$ 31,385	$ 40,996	$ 30,848	$ 25,655	$ 29,057	$ (22,483)	$ 126,051	$ 63,077	$ 49,370
Less: Income allocated to participating securities									123	89	36
Net income allocated to common shareholders									$ 125,928	$ 62,988	$ 49,334
Weighted average common shares outstanding Including participating securities									37,145	35,952	19,844
Less: Participating securities									36	50	20
Average common shares									37,109	35,902	19,824
Basic earnings per common share	$ 0.69	$ 0.76	$ 0.84	$ 1.10	$ 0.83	$ 0.69	$ 0.78	$ (0.71)	$ 3.39	$ 1.75	$ 2.49
Diluted Earnings Per Share:
Net income allocated to common shareholders									$ 125,928	$ 62,988	$ 49,334
Weighted average common shares outstanding for basic earnings per common share									37,109	35,902	19,824
Add: Dilutive effects of stock options and restricted stock units									91	47	107
Average shares and dilutive potential common shares									37,200	35,949	19,931
Diluted earnings per common share	$ 0.69	$ 0.76	$ 0.84	$ 1.10	$ 0.82	$ 0.69	$ 0.78	$ (0.71)	$ 3.39	$ 1.75	$ 2.48