Condensed MUFG Americas Holdings Corporation Unconsolidated Financial Statements (Parent Company) - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 2,457	$ 2,061
Other assets	10,200	9,620
Total assets	170,810	168,100	$ 154,550
Liabilities and Stockholders' Equity
Long-term debt	17,129	17,918
Other liabilities	2,837	2,048
Total liabilities	154,443	151,520
Stockholders' equity	16,367	16,580	$ 18,355	$ 17,386
Total liabilities and stockholders' equity	170,810	168,100
MUFG Americas Holdings Corporation
Assets
Cash and cash equivalents	840	739
Investments in and advances to subsidiaries: Bank subsidiary	18,103	18,493
Investments in and advances to subsidiaries: Nonbank subsidiaries	4,770	4,618
Other assets	407	76
Total assets	24,120	23,926
Liabilities and Stockholders' Equity
Long-term debt	7,622	7,355
Other liabilities	218	63
Total liabilities	7,840	7,418
Stockholders' equity	16,280	16,508
Total liabilities and stockholders' equity	24,120	23,926
Other Subsidiaries, Excluding MUFG Bank, NA [Member]
Liabilities and Stockholders' Equity
Long-term debt	$ 598	$ 931