v3.25.2
Accumulated Other Comprehensive Income (Reclassification of Significant Items out of Accumulated OCI) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Investment securities gains (losses)—net ¥ 832,533 ¥ (1,382,458) ¥ 256,941
Total before tax (1,795,576) (1,878,226) (461,312)
Income tax expense 527,938 500,657 46,751
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (1,267,638) (1,377,569) (414,561)
Equity in earnings of equity method investees—net or Other non-interest income (669,400) (464,054) (398,147)
Interest income on Loans, including fees (4,596,526) (4,362,986) (2,993,740)
Other non-interest expenses (533,961) (416,538) (439,780)
Other non-interest income (320,060) (163,603) (90,930)
Amount reclassified out of Accumulated OCI      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Total before tax 115,590 114,046 442,741
Income tax expense (35,580) (34,835) (127,829)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 80,010 79,211 314,912
Amount reclassified out of Accumulated OCI | Net losses (gains) on sales and redemptions of Available-for-sale debt securities      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Investment securities gains (losses)—net 150,567 149,292 (2,678)
Amount reclassified out of Accumulated OCI | Impairment losses on investment securities      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Investment securities gains (losses)—net 12,819 2 359,629
Amount reclassified out of Accumulated OCI | Gain on sale of MUFG Union Bank (Note 2)      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Investment securities gains (losses)—net 0 0 (28,251)
Other non-interest expenses (13,178) (11,664) 79,850
Amount reclassified out of Accumulated OCI | Gain on sale of MUFG Union Bank (Note 2) | Foreign exchange contracts      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Interest expense on Long-term debt or Foreign exchange gains (losses)—net 0 0 36,885
Amount reclassified out of Accumulated OCI | Net unrealized losses (gains) on investment securities      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Investment securities gains (losses)—net 3,596 1,352 8,617
Total before tax 166,982 150,646 337,317
Income tax expense (51,853) (45,320) (99,410)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 115,129 105,326 237,907
Amount reclassified out of Accumulated OCI | Net debt valuation adjustments      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Total before tax 1,538 776 444
Income tax expense (471) (237) (136)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 1,067 539 308
Equity in earnings of equity method investees—net or Other non-interest income 1,538 776 444
Amount reclassified out of Accumulated OCI | Net unrealized gains (losses) on derivatives qualifying for cash flow hedges:      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Total before tax 3,585 (8,197) 30,966
Income tax expense (717) 1,635 (8,448)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 2,868 (6,562) 22,518
Amount reclassified out of Accumulated OCI | Net unrealized gains (losses) on derivatives qualifying for cash flow hedges: | Interest rate contracts      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Interest income on Loans, including fees 0 0 (4,447)
Amount reclassified out of Accumulated OCI | Net unrealized gains (losses) on derivatives qualifying for cash flow hedges: | Foreign exchange contracts      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Interest expense on Long-term debt or Foreign exchange gains (losses)—net 3,585 (8,197) (1,472)
Amount reclassified out of Accumulated OCI | Net actuarial loss (gain)      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Other non-interest expenses (14,798) 1,962 9,135
Amount reclassified out of Accumulated OCI | Prior service cost      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Other non-interest expenses (2,059) (3,345) (4,942)
Amount reclassified out of Accumulated OCI | Gain on settlements and curtailment, and other      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Other non-interest expenses 0 0 14,395
Amount reclassified out of Accumulated OCI | Defined benefit plans      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Total before tax (30,034) (13,047) 98,438
Income tax expense 9,261 4,148 (27,315)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (20,773) (8,899) 71,123
Amount reclassified out of Accumulated OCI | Foreign currency translation adjustments      
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]      
Total before tax (26,481) (16,132) (24,424)
Income tax expense 8,200 4,939 7,480
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (18,281) (11,193) (16,944)
Other non-interest income ¥ (26,481) ¥ (16,132) ¥ (24,424)