v3.26.1
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
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
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 ¥ 147 ¥ (216)
Gains (losses) recognized in income on hedged item 0 (101) 335
Interest rate swap agreements | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income on derivative and other 0 0  
Interest rate swap agreements | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income on derivative and other (225) (91) 0
Gains (losses) recognized in income on hedged item 0 92 0
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 44,810 (6,028) (61,917)
Gains (losses) recognized in income on hedged item (44,917) 6,090 62,028
Foreign exchange contracts | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income on derivative and other 4,571 968  
Foreign exchange contracts | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income on derivative and other 9,183 (1,223) (130)
Gains (losses) recognized in income on hedged item ¥ (9,400) ¥ 959 ¥ 42