v3.26.1
Fair Value (Carrying Value of Assets Measured at Fair Value on Nonrecurring Basis by Level) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Goodwill ¥ 566,536 ¥ 558,164 ¥ 493,758
Fair Value, Measurements, Nonrecurring      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Investment securities 41,306 63,871  
Loans 276,108 277,573  
Loans held for sale 102,948 134,371  
Collateral dependent loans 173,160 143,202  
Premises and equipment 3,126 9,557  
Intangible assets 3,062 5,449  
Goodwill 242,644 161,758  
Other assets 56,822 53,438  
Investments in equity method investees 28,230 29,802  
Other 28,592 23,636  
Total 623,068 571,646  
Investment securities valued at net asset value 41,152 39,541  
Unfunded commitments related to investment securities valued at net asset value 46,682 34,847  
Fair Value, Measurements, Nonrecurring | Level 1      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Investment securities 0 0  
Loans 3,175 2,466  
Loans held for sale 0 0  
Collateral dependent loans 3,175 2,466  
Premises and equipment 0 0  
Intangible assets 0 0  
Goodwill 0 0  
Other assets 0 0  
Investments in equity method investees 0 0  
Other 0 0  
Total 3,175 2,466  
Fair Value, Measurements, Nonrecurring | Level 2      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Investment securities 20,079 14,041  
Loans 8,412 5,254  
Loans held for sale 0 0  
Collateral dependent loans 8,412 5,254  
Premises and equipment 0 0  
Intangible assets 0 0  
Goodwill 0 0  
Other assets 32,301 34,389  
Investments in equity method investees 26,039 27,745  
Other 6,262 6,644  
Total 60,792 53,684  
Fair Value, Measurements, Nonrecurring | Level 3      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Investment securities 21,227 49,830  
Loans 264,521 269,853  
Loans held for sale 102,948 134,371  
Collateral dependent loans 161,573 135,482  
Premises and equipment 3,126 9,557  
Intangible assets 3,062 5,449  
Goodwill 242,644 161,758  
Other assets 24,521 19,049  
Investments in equity method investees 2,191 2,057  
Other 22,330 16,992  
Total 559,101 515,496  
Fair value, recurring measurements      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Loans held for sale 29,024 28,447  
Total 115,513,860 96,224,960  
Fair value, recurring measurements | Marketable equity securities      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Contractual sale restriction equity security ¥ 69,713 ¥ 43,654  
Fair value, recurring measurements | Marketable equity securities | Minimum      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Contractual sale restriction equity security, remaining period 0 years 0 years  
Fair value, recurring measurements | Marketable equity securities | Maximum      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Contractual sale restriction equity security, remaining period 2 years 8 months 12 days 3 years  
Fair value, recurring measurements | Level 1      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Loans held for sale ¥ 0 ¥ 0  
Total 46,668,632 49,087,498  
Fair value, recurring measurements | Level 2      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Loans held for sale 29,024 28,447  
Total 65,410,495 44,006,257  
Fair value, recurring measurements | Level 3      
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]      
Loans held for sale 0 0  
Total ¥ 3,434,733 ¥ 3,131,205