v3.26.3
Derivative Financial Instruments and Hedging (Effect of Derivative Instruments on Consolidated Statements of Income, Pre-tax, Fair value hedges) (Detail) - Derivatives designated as hedging instruments - Fair value hedges - JPY (¥)
¥ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Interest rate swap agreements | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other   ¥ 0
Gains (losses) recognized in income on hedged item   0
Interest rate swap agreements | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other   0
Interest rate swap agreements | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other   (36)
Gains (losses) recognized in income on hedged item   (62)
Foreign exchange contracts | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other ¥ (10,047) 5,252
Gains (losses) recognized in income on hedged item 10,082 (5,217)
Foreign exchange contracts | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other 2,268 630
Foreign exchange contracts | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in income on derivative and other (2,160) (2,995)
Gains (losses) recognized in income on hedged item ¥ 2,076 ¥ 1,380