v3.26.1
Related Party Transactions - Summary of financial information of groups equity method investees (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Related Party Transaction [Line Items]      
Total assets ¥ 294,895,707 ¥ 276,741,152 ¥ 272,173,200
Total liabilities 283,417,654 266,191,227  
Total equity 11,478,053 10,549,924 10,431,187
Noncontrolling interests 618,420 484,909  
Total interest and dividend income 5,976,373 6,166,977 5,767,000
Net interest income after provision (credit) for credit losses 1,498,071 1,163,055 1,157,788
Income before income tax expense 1,685,600 759,300 1,623,100
Net income [1] 1,326,013 559,756 1,197,992
Equity Method Investee      
Related Party Transaction [Line Items]      
Loans 7,049,000 6,978,000  
Total assets 26,779,000 26,562,000  
Deposits 569,000 700,000  
Total liabilities 21,548,000 22,003,000  
Total equity 5,231,000 4,559,000  
Noncontrolling interests 34,000 26,000  
Total interest and dividend income 1,019,000 962,000 958,000
Total interest expense 380,000 323,000 384,000
Provision (credit) for credit losses 70,000 83,000 83,000
Net interest income after provision (credit) for credit losses 569,000 556,000 490,000
Income before income tax expense 545,000 474,000 394,000
Net income ¥ 407,000 ¥ 354,000 ¥ 298,000
[1] The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 16 “Accumulated other comprehensive income (loss), net of tax.”