Insurance Liabilities - Account Balances by Guaranteed Minimum Interest Rates (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 100,906	$ 102,899
Account balance percentage	100.00%	100.00%
At Guaranteed Minimum
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 53,230	$ 61,642
Account balance percentage	53.00%	60.00%
1 Basis Point - 50 Basis Points Above
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 6,885	$ 7,399
Account balance percentage	7.00%	7.00%
More than 50 Basis Points Above Minimum Guarantee
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 40,791	$ 33,858
Account balance percentage	40.00%	33.00%
Individual Retirement
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 57,354	$ 57,225
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	36,370	33,601
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	5,067	6,181
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	9,071	9,546
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	6,383	7,405
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	428	456
Individual Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	35	36
Individual Retirement | At Guaranteed Minimum
Policyholder Account Balance [Line Items]
Policyholder Account Balance	24,258	28,768
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	6,251	7,776
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	3,556	3,994
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	7,653	9,155
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	6,342	7,359
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	424	452
Individual Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	32	32
Individual Retirement | 1 Basis Point - 50 Basis Points Above
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,985	2,627
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,917	2,562
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	21	24
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	11	1
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	36	40
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Individual Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee
Policyholder Account Balance [Line Items]
Policyholder Account Balance	31,111	25,830
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	28,202	23,263
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,490	2,163
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,407	390
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	5	6
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	4	4
Individual Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	3	4
Group Retirement
Policyholder Account Balance [Line Items]
Policyholder Account Balance	36,427	38,324
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	11,700	10,825
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	5,393	6,266
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	12,011	13,601
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	603	658
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	6,579	6,821
Group Retirement | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	141	153
Group Retirement | At Guaranteed Minimum
Policyholder Account Balance [Line Items]
Policyholder Account Balance	24,739	28,261
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	2,133	2,063
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	3,597	5,005
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	11,686	13,561
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	603	658
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	6,579	6,821
Group Retirement | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	141	153
Group Retirement | 1 Basis Point - 50 Basis Points Above
Policyholder Account Balance [Line Items]
Policyholder Account Balance	3,236	3,661
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,895	2,713
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,126	908
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	215	40
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Group Retirement | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Group Retirement | More than 50 Basis Points Above Minimum Guarantee
Policyholder Account Balance [Line Items]
Policyholder Account Balance	8,452	6,402
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	7,672	6,049
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	670	353
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	110	0
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Group Retirement | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance
Policyholder Account Balance [Line Items]
Policyholder Account Balance	7,125	7,350
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	475	480
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,937	1,969
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,679	1,733
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	2,820	2,946
Life Insurance | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	214	222
Life Insurance | At Guaranteed Minimum
Policyholder Account Balance [Line Items]
Policyholder Account Balance	4,233	4,613
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	9	28
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,190	1,417
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	2,820	2,946
Life Insurance | At Guaranteed Minimum | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	214	222
Life Insurance | 1 Basis Point - 50 Basis Points Above
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,664	1,111
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	110	131
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,072	862
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	482	118
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | 1 Basis Point - 50 Basis Points Above | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | More than 50 Basis Points Above Minimum Guarantee
Policyholder Account Balance [Line Items]
Policyholder Account Balance	1,228	1,626
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range Less Than 1%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 1% To 2%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	365	349
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 2% To 3%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	856	1,079
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 3% To 4%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	7	198
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 4% To 5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	0	0
Life Insurance | More than 50 Basis Points Above Minimum Guarantee | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range From 5% To 5.5%
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 0	$ 0