Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank Common Stock	$ 38.0	$ 26.7
Federal Home Loan Bank, Advances	585.4	324.2
Federal Home Loan Bank, Collateral Posted to FHLB	1,879.6	1,461.8
Fixed Maturity Securities
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	754.9	553.6
Commercial Mortgage Loans
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	$ 1,124.7	$ 908.2

[Line Items] for Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Table]

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- Definition

Amount of advance from Federal Home Loan Bank (FHLBank).

+ References

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 470
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478878/942-470-45-1

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477734/942-470-50-3

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 325
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477974/942-325-45-1

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