Future Contract Benefit - Summary of Weighted-Average Interest Rates (Details)	Mar. 31, 2024	Mar. 31, 2023
Payout Annuities
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	3.90%	3.90%
Current discount rate	5.20%	4.90%
Traditional Life
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	5.00%	5.10%
Current discount rate	5.00%	4.80%
Group Protection
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	3.20%	2.90%
Current discount rate	5.00%	4.80%
UL and Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	5.30%	5.00%