Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of income taxes computed at the United States federal statutory tax rates
Tax at U.S. statutory rate	$ 46,794	$ 21,733	$ 45,294
Increase (decrease) in taxes resulting from:
Tax-exempt interest income	(1,669)	(1,431)	(1,205)
BOLI income	(1,547)	(1,182)	(1,283)
Investment tax credits	(988)	(1,494)	(1,863)
Amortization of investment in low-income housing tax credits	817	1,280	1,575
State income tax expense, net of federal benefit	2,479	469	5,509
Other items, net	1,049	465	64
Total income tax expense	$ 46,935	$ 19,840	$ 48,091