v3.26.3
Derivative Financial Instruments and Hedging (Effect of Derivative Instruments on Consolidated Statements of Income, Pre-tax, Cash flow hedges) (Detail) - Derivatives designated as hedging instruments - Cash flow hedges - JPY (¥)
¥ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Interest rate swap agreements    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in other comprehensive income on derivative ¥ 9,760 ¥ (2,575)
Interest rate swap agreements | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 0
Interest rate swap agreements | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income (286) (121)
Interest rate swap agreements | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 0
Foreign exchange contracts    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in other comprehensive income on derivative 182 298
Foreign exchange contracts | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 0
Foreign exchange contracts | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 945
Foreign exchange contracts | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 (4,017)
Foreign currency swap agreements    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in other comprehensive income on derivative (10,662) 5,174
Foreign currency swap agreements | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 0
Foreign currency swap agreements | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 773 1,124
Foreign currency swap agreements | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 6,085 (2,906)
Options held/written and other    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) recognized in other comprehensive income on derivative (3,873) (6,469)
Options held/written and other | Life insurance premiums and related investment income    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 152 50
Options held/written and other | Interest expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income 0 0
Options held/written and other | Other (income) and expense    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from other comprehensive income (loss) into income ¥ 0 ¥ 0