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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, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
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	$ 110,065	$ 80,893	$ 68,011
Change in taxes resulting from:
Tax-exempt interest income	(3,663)	(2,433)	(2,970)
State tax, net of federal income taxes and tax credit and refunds	4,808	4,094	3,966
Other investment income	(2,761)	(1,391)	(1,753)
Net investment expense, low-income housing investment	1,974	1,906	203
Other	1,321	(662)	948
Total income taxes	$ 111,744	$ 82,407	$ 68,405

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to net investment expense related to low income housing investments.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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