v3.26.1
Derivative Financial Instruments and Hedging (Effect of Derivative Instruments on Consolidated Statements of Income, Pre-tax) (Detail) - Fair value hedges - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Foreign exchange contracts | Life insurance premiums and related investment income      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income ¥ 17,327 ¥ 24,143 ¥ (25,208)
Foreign exchange contracts | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income ¥ (12) 14 31
Foreign exchange contracts | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income   0 0
Options held/written and other | Life insurance premiums and related investment income      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income   0 0
Options held/written and other | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income   0 0
Options held/written and other | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in income   ¥ 41 ¥ 57