Long-Duration Insurance Contracts - Actual and Expected Experience of Mortality Rate and Lapse Rate (Details)	Mar. 31, 2025	Mar. 31, 2024
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	1.00%	0.70%
Mortality / Morbidity, expected experience	0.80%	0.70%
Lapse rate, actual experience	3.10%	3.40%
Lapse rate, expected experience	3.70%	4.30%
Term Life | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	0.10%	0.10%
Mortality / Morbidity, expected experience	0.10%	0.10%
Lapse rate, actual experience	2.60%	3.60%
Lapse rate, expected experience	5.00%	5.10%
Term Life | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	0.10%	0.20%
Mortality / Morbidity, expected experience	0.50%	0.40%
Lapse rate, actual experience	3.80%	22.00%
Lapse rate, expected experience	5.10%	6.90%
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	2.30%	2.10%
Mortality / Morbidity, expected experience	1.90%	1.70%
Lapse rate, actual experience	3.30%	3.40%
Lapse rate, expected experience	3.00%	3.00%
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	0.40%	0.00%
Mortality / Morbidity, expected experience	0.30%	0.30%
Lapse rate, actual experience	3.80%	3.60%
Lapse rate, expected experience	4.00%	4.60%
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Mortality / Morbidity, actual experience	41.90%	39.90%
Mortality / Morbidity, expected experience	26.80%	26.30%
Lapse rate, actual experience	13.90%	12.00%
Lapse rate, expected experience	14.00%	13.80%