Insurance Liabilities (Future Policy Benefits - Reconciliation) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 31,870	$ 31,970
Liabilities reported in the preceding rollforward tables
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	20,211	20,048
Long-term care insurance (1)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	5,375	5,763
ULSG liabilities, including liability for profits followed by losses
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	2,591	2,654
Participating whole life insurance (2)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	2,875	2,729
Deferred profit liabilities
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	476	369
Other
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 342	$ 407