Future Policy Benefits (Undiscounted and Discounted) (Details) - Other Segments - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
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	$ 82,691	$ 82,288
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	189,341	181,123
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	81,087	80,478
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	179,131	172,081
Americas [Member] | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	1,829	1,975
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	14,071	9,214
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	8,296	5,408
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	2,914	3,112
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	21,591	21,317
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	56,998	56,223
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	21,670	21,289
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	55,118	53,244
CANADA | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	2,900	3,149
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	4,128	4,602
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	2,738	3,062
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	4,390	4,738
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	14,388	13,611
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	25,709	24,150
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	13,774	12,889
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	25,928	24,591
EMEA [Member] | Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	55,187	37,636
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	100,423	66,775
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	56,214	39,070
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	98,292	64,424
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	38,412	37,986
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	90,670	88,496
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	32,824	32,313
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	94,316	92,305
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	2,840	2,478
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	17,399	10,144
Liability For Future Policy Benefit Expected Future Policy Benefit Discounted Before Reinsurance	11,499	7,472
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 3,743	$ 2,977