Condensed MUFG Americas Holdings Corporation Unconsolidated Financial Statements (Parent Company) - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 2,061	$ 2,057
Other assets	9,620	9,410
Total assets	168,100	154,550	$ 148,144
Liabilities and Stockholders' Equity
Long-term debt	17,918	12,162
Other liabilities	2,048	2,143
Total liabilities	151,520	136,195
Stockholders' equity	16,580	18,355	$ 17,386	$ 16,593
Total liabilities and stockholders' equity	168,100	154,550
MUFG Americas Holdings Corporation
Assets
Cash and cash equivalents	739	1,341
Investments in and advances to subsidiaries: Bank subsidiary	18,493	19,598
Investments in and advances to subsidiaries: Nonbank subsidiaries	4,618	4,314
Other assets	76	69
Total assets	23,926	25,322
Liabilities and Stockholders' Equity
Long-term debt	7,355	6,997
Other liabilities	63	70
Total liabilities	7,418	7,067
Stockholders' equity	16,508	18,255
Total liabilities and stockholders' equity	23,926	25,322
Other Subsidiaries, Excluding MUFG Bank, NA [Member]
Liabilities and Stockholders' Equity
Long-term debt	$ 931	$ 1,355