Income Taxes - Components of Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amount
Statutory federal income tax	$ 28,346	$ 55,847	$ 41,382
State income tax, net of federal income tax effect	3,125	14,172	8,846
Tax-exempt income, net of interest expense disallowance	(2,589)	(3,234)	(3,104)
Deferred tax asset revaluation	0	0	(8,721)
Other	(1,799)	(584)	784
Total income tax expense	$ 27,083	$ 66,201	$ 39,187
% of Pretax Income
Statutory federal income tax rate (percent of pretax income)	21.00%	21.00%	21.00%
State income tax, net of federal income tax effect (percent of pretax income)	2.30%	5.30%	4.50%
Tax-exempt income, net of interest expense disallowance (percent of pretax income)	(1.90%)	(1.20%)	(1.60%)
Deferred tax asset revaluation (percent of pretax income)	0.00%	0.00%	(4.40%)
Other (percent of pretax income)	(1.30%)	(0.20%)	0.40%
Effective tax rate	20.10%	24.90%	19.90%