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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, 2021	Dec. 31, 2020	Dec. 31, 2019
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	$ 68,011	$ 45,218	$ 55,086
Change in taxes resulting from:
Tax-exempt interest income	(2,970)	(2,709)	(2,550)
State tax, net of federal income taxes and tax credit and refunds	3,966	2,622	2,587
Other investment income	(1,753)	(2,205)	(1,480)
Net investment expense, low income housing investment	203	1,990	623
Other	948	(477)	584
Total income taxes	$ 68,405	$ 44,439	$ 54,850

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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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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the current period and the expected income tax expense or benefit computed attributable to other investment income.

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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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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 state and local income tax expense (benefit).

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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 income (loss) exempt from income taxes.

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