v3.26.1
Other Assets and Liabilities (Summarized Financial Information of Morgan Stanley) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Schedule of Equity Method Investments [Line Items]      
Total assets ¥ 425,581,652 ¥ 405,940,211 ¥ 397,820,570
Total liabilities 404,741,595 386,690,473  
Noncontrolling interests 1,266,924 964,252  
Equity Method Investment, Summarized Financial Information, Income and Loss      
Net income applicable to Morgan Stanley 1,883,904 1,267,638 1,377,569
Morgan Stanley      
Schedule of Equity Method Investments [Line Items]      
Trading assets 84,131,000 59,844,000  
Securities purchased under agreements to resell 20,605,000 17,800,000  
Securities borrowed 24,713,000 20,967,000  
Total assets 252,837,000 194,420,000  
Deposits 68,424,000 57,051,000  
Customer and other payables 41,455,000 30,163,000  
Borrowings 59,406,000 45,662,000  
Total liabilities 234,390,000 178,295,000  
Noncontrolling interests 176,000 155,000  
Equity Method Investment, Summarized Financial Information, Income and Loss      
Net revenues 11,081,000 9,739,000 7,907,000
Total non-interest expenses 7,498,000 6,843,000 6,068,000
Income from continuing operations before income taxes 3,536,000 2,835,000 1,798,000
Net income applicable to Morgan Stanley ¥ 2,736,000 ¥ 2,162,000 ¥ 1,375,000