Segment Information - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember, srt:PresidentMember
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	Our chief operating decision maker, the President and Chief Executive Officer, evaluates segment operating results through Income before income taxes. In assessing segment results and determining the allocations of resources, factors such as operating trends, period-over-period analytical comparisons, and budget-to-actual variances are considered.
Percentage of voluntary protection contract revenues	86.00%	84.00%
Unearned amounts in voluntary protection contract revenues, recognized	$ 945	$ 869
Other liabilities [Member]
Segment Reporting Information [Line Items]
Unearned voluntary protection contract revenues	$ 3,400	$ 3,100	$ 2,900
Minimum [Member]
Segment Reporting Information [Line Items]
Insurance Policy Term	3 months
Maximum [Member]
Segment Reporting Information [Line Items]
Insurance Policy Term	120 months