Future Contract Benefits - Summary of Discounted and Undiscounted Expected Future Benefit Payments (Group Protection) (Details) - Group Protection - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Undiscounted
Expected future benefit payments	$ 7,486	$ 7,154
Discounted
Expected future benefit payments	$ 5,794	$ 5,773

Liability For Future Policy Benefit, Discounted, Befiore Reinsurance

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- Definition

Liability for future policy benefit, expected future policy benefit, discounted, before reinsurance.

+ References

No definition available.

+ Details

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- Definition

Liability For Future Policy Benefit, Undiscounted, Befiore Reinsurance

+ References

No definition available.

+ Details

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- Definition

Amount, before effect of reinsurance, of undiscounted balance for expected future policy benefit and expense component of liability for future policy benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-6

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29E

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