Insurance Liabilities - Expected Future Benefits, Expenses, and Gross Premiums (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
General Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	$ 2,911	$ 3,350
Undiscounted expected future gross premiums	4,002	4,616
Discounted expected future gross premiums (at current discount rate)	2,900
Individual Retirement
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	2,156	2,048
Undiscounted expected future gross premiums	0	0
Group Retirement
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	309	317
Undiscounted expected future gross premiums	0	0
Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	40,741	39,028
Undiscounted expected future gross premiums	30,656	28,964
Discounted expected future gross premiums (at current discount rate)	20,000
Institutional Markets
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	42,519	29,029
Undiscounted expected future gross premiums	0	0
Other Operations
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits and expense	42,701	44,148
Undiscounted expected future gross premiums	2,106	$ 2,225
Discounted expected future gross premiums (at current discount rate)	$ 1,400