BUSINESS SEGMENT AND FOREIGN INFORMATION - Yen/Dollar Exchange Rates Used (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2022 USD ($) ¥ / $	Dec. 31, 2021 USD ($) ¥ / $	Dec. 31, 2020 USD ($) ¥ / $
Segment Reporting, Other Significant Reconciling Item [Line Items]
Weighted-average yen/dollar exchange rate | ¥ / $	[1]	130.17	109.79	106.86
Yen percent strengthening (weakening)		(15.70%)	(2.70%)	2.10%
Exchange effect on pretax operating earnings (in millions)		$ (263)	$ (47)	$ 38
Yen/dollar exchange rate at December 31 | ¥ / $	[1]	132.70	115.02
Yen percent strengthening (weakening)		(13.30%)	(10.00%)
Exchange effect on total assets
Segment Reporting, Other Significant Reconciling Item [Line Items]
Exchange effect		$ (10,936)	$ (9,635)
Exchange effect on total liabilities
Segment Reporting, Other Significant Reconciling Item [Line Items]
Exchange effect		$ (9,589)	$ (7,566)

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