Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income Attributable to MUAH	$ 344	[1]	$ 295	[1]	$ 510	$ 524
Other Comprehensive Income (Loss), Net of Tax:
Net change in unrealized gains (losses) on cash flow hedges	(8)		22		(66)	(8)
Net change in unrealized gains (losses) on investment securities	(41)		24		(231)	59
Foreign currency translation adjustment	0		2		(2)	3
Pension and other postretirement benefit adjustments	10		6		20	13
Other	0		0		(1)	0
Total other comprehensive income (loss)	(39)		54		(280)	67
Comprehensive Income (Loss) Attributable to MUAH	305		349		230	591
Comprehensive income (loss) from noncontrolling interests	(15)		(10)		(14)	(15)
Total Comprehensive Income (Loss)	$ 290		$ 339		$ 216	$ 576

[1] As of and for the Three Months Ended June 30, 2018:(Dollars in millions) Regional Bank U.S. Wholesale & Investment Banking Transaction Banking MUSA Other MUFG Americas Holdings CorporationResults of operations Net interest income $540 $101 $67 $51 $66 $825Noninterest income 116 98 15 77 290 596Total revenue 656 199 82 128 356 1,421Noninterest expense 532 103 65 116 267 1,083(Reversal of) provision for credit losses (5) (5) — — (9) (19)Income (loss) before income taxes and including noncontrolling interests 129 1011712 98357Income tax expense (benefit) (1) 26 (4) 4 3 (1) 28Net income (loss) including noncontrolling interests 103 105 13 9 99 329Deduct: net (income) loss from noncontrolling interests — — — — 15 15Net income (loss) attributable to MUAH $103 $105 $13 $9 $114 $344 Total assets, end of period $70,186 $19,740 $991 $32,904 $36,552 $160,373