Pension and Postretirement Benefit Costs - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2023	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Liability for Future Policy Benefits, Individual and Group Annuities and Supplementary Contracts		$ 500.0
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Funding threshold	80.00%
Defined Benefit Plan, Benefit Obligation, Payment for Settlement	$ 442.0

Percentage of company's qualified pension plans on a GAAP accounting basis.

No definition available.

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- Definition

Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(10)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Amount of accrued obligation to policyholders that relates to insured events under individual and group annuities and supplementary insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(13)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 25
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479250/944-40-25-11

+ Details

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Balance Type:	credit
Period Type:	instant

- Details

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