BUSINESS SEGMENT INFORMATION AND SELECTED FOREIGN CURRENCY TRANSLATION ITEMS - Yen/Dollar Exchange Rates Used (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2025 USD ($) ¥ / $	Dec. 31, 2024 USD ($) ¥ / $	Dec. 31, 2023 USD ($) ¥ / $
Segment Reporting, Other Significant Reconciling Item [Line Items]
Weighted-average yen/dollar exchange rate | ¥ / $	[1]	149.32	150.97	140.57
Yen percent strengthening (weakening)		1.10%	(6.90%)	(7.40%)
Exchange effect on pretax adjusted earnings (in millions)		$ 24	$ (125)	$ (131)
Yen/dollar exchange rate at December 31 | ¥ / $	[1]	156.56	158.18
Yen percent strengthening (weakening)		1.00%	(10.30%)
Exchange effect on total assets
Segment Reporting, Other Significant Reconciling Item [Line Items]
Exchange effect		$ 878	$ (6,127)
Exchange effect on total liabilities
Segment Reporting, Other Significant Reconciling Item [Line Items]
Exchange effect		$ (2,159)	$ (9,624)

[1] Rates are based on the published MUFG Bank, Ltd. telegraphic transfer middle rate (TTM).