v3.26.1
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
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Interest rate swap agreements      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in other comprehensive income on derivative ¥ 7,176 ¥ (2,226) ¥ (5,090)
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 0
Interest rate swap agreements | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) reclassified from other comprehensive income (loss) into income (1,186) (446) (114)
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 0
Foreign exchange contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in other comprehensive income on derivative 1,141 2,179 (57)
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 0
Foreign exchange contracts | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) reclassified from other comprehensive income (loss) into income 946 694 0
Foreign exchange contracts | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) reclassified from other comprehensive income (loss) into income (4,017) 0 0
Foreign currency swap agreements      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in other comprehensive income on derivative 5,447 (10,239) 2,733
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 0
Foreign currency swap agreements | Interest expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) reclassified from other comprehensive income (loss) into income 2,720 2,977 2,521
Foreign currency swap agreements | Other (income) and expense      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) reclassified from other comprehensive income (loss) into income (1,764) 8,262 (6,299)
Options held/written and other      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recognized in other comprehensive income on derivative (12,412) (8,059) (1,092)
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 125 14 0
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 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 ¥ 0