Long-Duration Insurance Contracts - Actual and Expected Experience of Mortality Rate and Lapse Rate (Details)	Mar. 31, 2024	Mar. 31, 2023
Whole Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality, actual experience	0.70%	0.70%
Mortality, expected experience	0.70%	0.70%
Lapse rate, actual experience	3.40%	3.60%
Lapse rate, expected experience	4.30%	4.60%
Term Life Insurance | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality, actual experience	0.10%	0.10%
Mortality, expected experience	0.10%	0.10%
Lapse rate, actual experience	3.60%	5.60%
Lapse rate, expected experience	5.10%	2.80%
Term Life Insurance | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality, actual experience	0.20%	0.30%
Mortality, expected experience	0.40%	0.60%
Lapse rate, actual experience	22.00%	8.30%
Lapse rate, expected experience	6.90%	5.60%
Experience Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality, actual experience	2.10%	1.90%
Mortality, expected experience	1.70%	1.60%
Lapse rate, actual experience	3.40%	3.40%
Lapse rate, expected experience	3.00%	3.00%
Limited Pay Whole Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality, actual experience	0.00%	0.00%
Mortality, expected experience	0.30%	0.20%
Lapse rate, actual experience	3.60%	3.60%
Lapse rate, expected experience	4.60%	5.10%