Condensed MUFG Americas Holdings Corporation Unconsolidated Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities:
Net income	$ 573	$ 816	$ 647
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Other, net	(24)	21	(37)
Cash Flows from Financing Activities:
Capital contribution from BTMU	0	0	1,200
Other, net	(61)	(25)	(25)
Net change in cash and cash equivalents	(1,222)	(452)	712
Cash and cash equivalents at beginning of period	5,751	6,203	5,491
Cash and cash equivalents at end of period	4,529	5,751	6,203
MUFG Americas Holdings Corporation
Cash Flows from Operating Activities:
Net income	573	816	647
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Equity in undistributed net (income) loss of subsidiaries	(609)	(831)	(668)
Other, net	9	1	14
Net cash provided by (used in) operating activities	(27)	(14)	(7)
Cash Flows from Investing Activities:
Investments in and advances to subsidiaries	(2,070)	0	(1,700)
Repayment of investments in and advances to subsidiaries	7	165	35
Net cash used in investing activities	(2,063)	165	(1,665)
Cash Flows from Financing Activities:
Capital contribution from BTMU	0	0	1,200
Proceeds from issuance of subordinated loan due to BTMU	0	0	300
Proceeds from issuance of senior debt	2,197	0	0
Repayment of subordinated debt	(17)	0	(400)
Repayment of junior subordinated debt	0	(14)	0
Other, net	(11)	0	0
Net cash provided by (used in) financing activities	2,169	(14)	1,100
Net change in cash and cash equivalents	79	137	(572)
Cash and cash equivalents at beginning of period	328	191	763
Cash and cash equivalents at end of period	$ 407	$ 328	$ 191