v3.26.3
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
Sep. 30, 2026
Mar. 31, 2026
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value ¥ 126,433 ¥ 154,513
Derivative liabilities, Fair value 93,669 118,058
Interest rate swap agreements | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 541,023 615,793
Interest rate swap agreements | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 28,839 26,273
Interest rate swap agreements | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 1,802 2,287
Interest rate swap agreements | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 16,579 2,274
Interest rate swap agreements | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 119 85
Interest rate swap agreements | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 59 2
Options held/written and other | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 88,466 76,234
Options held/written and other | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 361 0
Options held/written and other | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 17,129 15,426
Options held/written and other | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 877,893 774,332
Options held/written and other | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 34,258 17,402
Options held/written and other | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 20,914 6,117
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 1,121,027 1,048,627
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 11,282 3,704
Futures, foreign exchange contracts | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 23,369 70,789
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 1,727,413 [1] 1,284,971 [2]
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 24,679 [1] 65,959 [2]
Futures, foreign exchange contracts | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 24,213 [1] 23,402 [2]
Foreign currency swap agreements | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 482,102 482,092
Foreign currency swap agreements | Derivatives designated as hedging instruments and other | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 26,895 41,090
Foreign currency swap agreements | Derivatives designated as hedging instruments and other | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value 6,170 12
Foreign currency long-term debt | Derivatives designated as hedging instruments and other    
Derivatives, Fair Value [Line Items]    
Notional amount 81,968 83,286
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 held/written | Derivatives not designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Notional amount 1,169 1,372
Credit derivatives held/written | Derivatives not designated as hedging instruments | Other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, Fair value 0 0
Credit derivatives held/written | Derivatives not designated as hedging instruments | Other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, Fair value ¥ 13 ¥ 23
[1] The notional amounts of futures and foreign exchange contracts in the above table include futures contracts of ¥940 million and foreign exchange contracts of ¥600 million to economically hedge the minimum guarantee risk of variable annuity and variable life insurance contracts at September 30, 2026, respectively. Derivative assets in the above table include fair value of the futures and foreign exchange contracts before offsetting of ¥4 million and ¥4 million and derivative liabilities include fair value of the futures and foreign exchange contracts before offsetting of ¥13 million and ¥2 million at September 30, 2026, respectively.
[2] 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.