v3.26.1
Commitments, Guarantees, and Contingent Liabilities (Summary of Potential Future Payments, Book Value Recorded as Guarantee Liabilities of Guarantee Contracts Outstanding and Maturity of Longest Guarantee Contracts) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Guarantor Obligations [Line Items]    
Potential future payment ¥ 1,248,532 ¥ 1,123,984
Book value of guarantee liabilities 19,718 12,276
Transferred loans    
Guarantor Obligations [Line Items]    
Potential future payment 609,536 543,453
Book value of guarantee liabilities ¥ 13,760 ¥ 6,918
Maturity of the longest contract (Years) 2062 2062
Real estate loans    
Guarantor Obligations [Line Items]    
Potential future payment ¥ 6,524 ¥ 8,408
Book value of guarantee liabilities ¥ 0 ¥ 135
Maturity of the longest contract (Years) Undetermined 2048
Other    
Guarantor Obligations [Line Items]    
Potential future payment ¥ 18,225 ¥ 13,261
Book value of guarantee liabilities ¥ 0 ¥ 0
Maturity of the longest contract (Years) 2043 2044
Corporate loans    
Guarantor Obligations [Line Items]    
Potential future payment ¥ 614,247 ¥ 558,862
Book value of guarantee liabilities ¥ 5,958 ¥ 5,223
Maturity of the longest contract (Years) 2033 2031