v3.26.1
Fair Value (Summary of Carrying Amounts and Estimated Fair Values of Financial Instruments Not Carried at Fair Value on Recurring Basis on Balance Sheets by Level) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Financial liabilities:    
Carrying amounts of investments in equity method investees ¥ 5,461,950 ¥ 4,564,269
Carrying amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and due from banks 4,367,000 4,591,000
Interest-earning deposits in other banks 86,003,000 104,707,000
Call loans and funds sold 2,170,000 1,676,000
Receivables under resale agreements 16,885,000 18,782,000
Receivables under securities borrowing transactions 5,493,000 5,701,000
Investment securities 26,013,000 23,272,000
Loans, net of allowance for credit losses 143,562,000 130,187,000
Other financial assets 12,774,000 9,783,000
Financial liabilities:    
Non-interest-bearing 35,860,000 36,820,000
Interest-bearing 224,956,000 212,633,000
Total deposits 260,816,000 249,453,000
Call money and funds purchased 5,257,000 5,017,000
Payables under repurchase agreements 39,516,000 43,664,000
Payables under securities lending transactions 1,252,000 718,000
Due to trust account and other short-term borrowings 14,633,000 28,229,000
Long-term debt 21,870,000 20,928,000
Other financial liabilities 9,595,000 9,038,000
Carrying amounts of investments in equity method investees 4,564,000 5,462,000
Estimated fair value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and due from banks 4,367,000 4,591,000
Interest-earning deposits in other banks 86,003,000 104,707,000
Call loans and funds sold 2,170,000 1,676,000
Receivables under resale agreements 16,885,000 18,782,000
Receivables under securities borrowing transactions 5,493,000 5,701,000
Investment securities 24,893,000 22,647,000
Loans, net of allowance for credit losses 142,235,000 129,772,000
Other financial assets 12,774,000 9,783,000
Financial liabilities:    
Non-interest-bearing 35,860,000 36,820,000
Interest-bearing 224,788,000 212,643,000
Total deposits 260,648,000 249,463,000
Call money and funds purchased 5,257,000 5,017,000
Payables under repurchase agreements 39,516,000 43,664,000
Payables under securities lending transactions 1,252,000 718,000
Due to trust account and other short-term borrowings 14,633,000 28,229,000
Long-term debt 21,018,000 20,199,000
Other financial liabilities 9,595,000 9,038,000
Estimated fair value | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and due from banks 4,367,000 4,591,000
Interest-earning deposits in other banks 0 0
Call loans and funds sold 0 0
Receivables under resale agreements 0 0
Receivables under securities borrowing transactions 0 0
Investment securities 14,567,000 12,932,000
Loans, net of allowance for credit losses 3,000 2,000
Other financial assets 0 0
Financial liabilities:    
Non-interest-bearing 0 0
Interest-bearing 0 0
Total deposits 0 0
Call money and funds purchased 0 0
Payables under repurchase agreements 0 0
Payables under securities lending transactions 0 0
Due to trust account and other short-term borrowings 0 0
Long-term debt 0 0
Other financial liabilities 0 0
Estimated fair value | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and due from banks 0 0
Interest-earning deposits in other banks 86,003,000 104,707,000
Call loans and funds sold 2,170,000 1,676,000
Receivables under resale agreements 16,885,000 18,782,000
Receivables under securities borrowing transactions 5,493,000 5,701,000
Investment securities 8,483,000 8,244,000
Loans, net of allowance for credit losses 112,000 70,000
Other financial assets 12,774,000 9,783,000
Financial liabilities:    
Non-interest-bearing 35,860,000 36,820,000
Interest-bearing 224,788,000 212,643,000
Total deposits 260,648,000 249,463,000
Call money and funds purchased 5,257,000 5,017,000
Payables under repurchase agreements 39,516,000 43,664,000
Payables under securities lending transactions 1,252,000 718,000
Due to trust account and other short-term borrowings 14,633,000 28,229,000
Long-term debt 21,018,000 20,199,000
Other financial liabilities 9,595,000 9,038,000
Estimated fair value | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and due from banks 0 0
Interest-earning deposits in other banks 0 0
Call loans and funds sold 0 0
Receivables under resale agreements 0 0
Receivables under securities borrowing transactions 0 0
Investment securities 1,843,000 1,471,000
Loans, net of allowance for credit losses 142,120,000 129,700,000
Other financial assets 0 0
Financial liabilities:    
Non-interest-bearing 0 0
Interest-bearing 0 0
Total deposits 0 0
Call money and funds purchased 0 0
Payables under repurchase agreements 0 0
Payables under securities lending transactions 0 0
Due to trust account and other short-term borrowings 0 0
Long-term debt 0 0
Other financial liabilities ¥ 0 ¥ 0