Condensed MUFG Americas Holdings Corporation Unconsolidated Financial Statements (Parent Company) - Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income:
Total income	$ 5,798	$ 5,484	$ 5,214
Expense:
Other expense	6,215	4,277	3,984
Income before income taxes and including noncontrolling interests	(669)	1,101	1,333
Income tax benefit	(82)	(52)	(299)
Equity in undistributed net income of subsidiaries less dividends received:
Net (Loss) Income Including Noncontrolling Interests	(751)	1,049	1,034
MUFG Americas Holdings Corporation
Income:
Interest income on advances to subsidiaries and deposits in bank	161	137	79
Rental Income	15	15	15
Total income	792	1,947	465
Expense:
Interest expense	251	194	144
Other expense	29	17	14
Total expense	280	211	158
Income before income taxes and including noncontrolling interests	512	1,736	307
Income tax benefit	24	13	20
Income (loss) before equity in undistributed net income of subsidiaries	536	1,749	327
Equity in undistributed net income of subsidiaries less dividends received:
Bank subsidiary	(746)	(697)	366
Nonbank subsidiaries	(524)	21	384
Net (Loss) Income Including Noncontrolling Interests	(734)	1,073	1,077
Bank Subsidiary | MUFG Americas Holdings Corporation
Income:
Investment Income, Dividend	0	1,700	320
Nonbank Subsidiary | MUFG Americas Holdings Corporation
Income:
Investment Income, Dividend	$ 616	$ 95	$ 51