Income Taxes (Income Tax Expense Differences from the Amount Computed by Applying the U.S. Federal Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
U.S. Federal income tax rate (as a percent)	21.00%	21.00%	21.00%
Reasons for the difference of income tax expense
Computed expected tax expense	$ 80,893	$ 68,011	$ 45,218
Change in taxes resulting from:
Tax-exempt interest income	(2,433)	(2,970)	(2,709)
State tax, net of federal income taxes and tax credit and refunds	4,094	3,966	2,622
Other investment income	(1,391)	(1,753)	(2,205)
Net investment expense, low-income housing investment	1,906	203	1,990
Other	(662)	948	(477)
Total income taxes	$ 82,407	$ 68,405	$ 44,439