v3.26.1
Foreign Activities (Consolidated Income Statement and Total Assets Information by Major Geographic Area) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Segment Reporting Information [Line Items]      
Total revenue [1] ¥ 8,794,500 ¥ 8,169,900 ¥ 8,510,700
Total expenses [2] 7,108,900 7,410,600 6,887,600
Income before income tax expense 1,685,600 759,300 1,623,100
Net income (loss) [3] 1,326,013 559,756 1,197,992
Total assets 294,895,707 276,741,152 272,173,200
Japan      
Segment Reporting Information [Line Items]      
Total revenue [1] 3,467,900 2,151,300 2,827,100
Total expenses [2] 3,226,200 2,681,200 2,171,800
Income before income tax expense 241,800 (529,900) 655,300
Net income (loss) 62,100 (521,500) 449,000
Total assets 175,801,600 171,683,900 170,063,800
United States of America      
Segment Reporting Information [Line Items]      
Total revenue [1] 3,299,500 3,724,500 3,584,400
Total expenses [2] 2,110,300 2,701,800 2,978,700
Income before income tax expense 1,189,200 1,022,700 605,600
Net income (loss) 1,112,300 926,300 491,100
Total assets 64,059,600 58,654,100 57,036,000
Others      
Segment Reporting Information [Line Items]      
Total revenue [1] 226,200 246,900 198,500
Total expenses [2] 211,800 297,000 191,600
Income before income tax expense 14,400 (50,100) 6,800
Net income (loss) 5,500 (59,000) (1,600)
Total assets 5,035,800 3,990,200 4,483,000
Europe      
Segment Reporting Information [Line Items]      
Total revenue [1] 795,600 840,600 803,700
Total expenses [2] 793,600 902,200 817,100
Income before income tax expense 2,100 (61,600) (13,300)
Net income (loss) (25,900) (91,100) (50,000)
Total assets 23,341,100 19,835,400 19,142,100
Asia/Oceania excluding Japan, and others      
Segment Reporting Information [Line Items]      
Total revenue [1] 1,005,300 1,206,600 1,097,100
Total expenses [2] 767,100 828,400 728,400
Income before income tax expense 238,200 378,200 368,600
Net income (loss) 172,000 305,100 309,500
Total assets ¥ 26,657,600 ¥ 22,577,700 ¥ 21,448,200
[1] Total revenue is comprised of Interest and dividend income and Noninterest income.    
[2] Total expenses are comprised of Interest expense, Provision (credit) for credit losses and Noninterest expenses. 
[3] 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.”