v3.26.1
Derivative Financial Instruments and Hedging (Notional Amounts of Derivative Instruments and Other, Fair Values of Derivative Instruments and Other before Offsetting) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value ¥ 154,513 ¥ 64,170
Derivative liabilities, Fair value 118,061 56,038
Interest rate swap agreements | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 615,793 676,691
Interest rate swap agreements | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 26,273 17,788
Interest rate swap agreements | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 2,287 2,768
Interest rate swap agreements | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 2,274 1,477
Interest rate swap agreements | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 85 81
Interest rate swap agreements | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 2 6
Options held/written and other | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 76,234 94,608
Options held/written and other | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 0 98
Options held/written and other | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 15,426 7,323
Options held/written and other | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 774,332 582,939
Options held/written and other | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 17,402 15,669
Options held/written and other | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 6,117 6,392
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 1,048,627 932,649
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 3,704 9,515
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 70,789 25,445
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 1,285,303 [1] 1,592,590 [2]
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 65,959 [1] 11,449 [2]
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 23,405 [1] 13,942 [2]
Foreign currency swap agreements | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 482,092 303,060
Foreign currency swap agreements | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 41,090 9,570
Foreign currency swap agreements | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 12 159
Foreign currency long-term debt | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 83,286 250,702
Foreign currency long-term debt | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 0 0
Foreign currency long-term debt | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 0 0
Credit derivatives written | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount   1,000
Credit derivatives written | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value   0
Credit derivatives written | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value   ¥ 3
Credit derivatives held/written | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 1,372  
Credit derivatives held/written | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 0  
Credit derivatives held/written | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value ¥ 23  
[1] The notional amounts of futures and foreign exchange contracts in the above table include futures contracts of ¥1,741 million and foreign exchange contracts of ¥964 million to economically hedge the minimum guarantee risk of variable annuity and variable life insurance contracts at March 31, 2026, respectively. Derivative assets in the above table include fair value of the futures and foreign exchange contracts before offsetting of ¥47 million and ¥8 million and derivative liabilities include fair value of the futures and foreign exchange contracts before offsetting of ¥6 million and ¥23 million at March 31, 2026, respectively.
[2] The notional amounts of futures and foreign exchange contracts in the above table include futures contracts of ¥5,575 million and foreign exchange contracts of ¥2,205 million to economically hedge the minimum guarantee risk of variable annuity and variable life insurance contracts at March 31, 2025, respectively. Derivative assets in the above table include fair value of the futures and foreign exchange contracts before offsetting of ¥38 million and ¥38 million and derivative liabilities include fair value of the futures and foreign exchange contracts before offsetting of ¥57 million and ¥11 million at March 31, 2025, respectively.