Borrowings and Financing Activities - Narrative (Details) - USD ($)	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Debt Securities \| Fixed-maturities available for sale
Debt Instrument [Line Items]
Investments serving as collateral for FHLB advances	$ 163,900,000	$ 167,300,000
Senior notes
Debt Instrument [Line Items]
Mortgage financing facilities outstanding	$ 1,413,504,000	$ 1,409,473,000
Senior notes \| Senior Notes Due 2024, 2025 and 2027
Debt Instrument [Line Items]
Redemption price, percentage of principal amount	100.00%
Basis spread on variable rate	0.50%
Stock retention percentage required in order to make capital stock transactions	80.00%
FHLB advances
Debt Instrument [Line Items]
FHLB maturity period	90 days
Federal Home Loan Bank certificates and obligations \| Minimum
Debt Instrument [Line Items]
FHLB ratio of market value to collateral advances	1.03
Federal Home Loan Bank certificates and obligations \| Maximum
Debt Instrument [Line Items]
FHLB ratio of market value to collateral advances	1.14
Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, higher borrowing capacity option	$ 400,000,000
Line of credit facility, fair value of amount outstanding	0
Revolving credit facility \| Unsecured revolving credit facility, expiration date 2026
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	275,000,000
Mortgages \| Mortgage financing facilities
Debt Instrument [Line Items]
Mortgage financing facilities outstanding	$ 2,100,000

The ratio of the market value of the collateralized eligible assets to the principal balance of the FHLB advances

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Line of Credit Facility, Accordion Feature, Higher Borrowing Capacity Option

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- Definition

Percent Of Stock With Ordinary Voting Rights That Company Must Retain In Order To Make Any Capital Stock Transactions

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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Maturity period on fixed rate advances made and reported by Federal Home Loan Bank (FHLBank), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Fair value of the amount outstanding under the credit facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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