Future Policy Benefits (Undiscounted and Discounted) (Details) - Other Segments - USD ($) $ in Millions	Mar. 31, 2025	Mar. 31, 2024
Americas [Member] | Life Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	$ 84,218	$ 82,691
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	196,448	189,341
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	83,212	81,087
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	183,915	179,131
Americas [Member] | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	1,666	1,829
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	22,679	14,071
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	10,940	8,296
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	2,648	2,914
CANADA | Life Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	21,326	21,591
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	53,586	56,998
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	21,304	21,670
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	52,094	55,118
CANADA | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	3,768	2,900
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	17,252	4,128
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	7,993	2,738
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	5,689	4,390
EMEA [Member] | Life Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	15,240	14,388
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	28,718	25,709
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	14,829	13,774
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	28,701	25,928
EMEA [Member] | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	65,091	55,187
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	139,460	100,423
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	70,120	56,214
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	129,865	98,292
Asia Pacific [Member] | Life Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	42,040	38,412
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	101,929	90,670
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	35,804	32,824
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	104,940	94,316
Asia Pacific [Member] | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	3,707	2,840
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	27,778	17,399
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	14,570	11,499
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 5,292	$ 3,743