Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income Attributable to MUAH	$ 232	[1]	$ 260	[2]	$ 756	[3]	$ 656	[4]
Other Comprehensive Income (Loss), Net of Tax:
Net change in unrealized gains (losses) on cash flow hedges	(3)		(59)		(11)		131
Net change in unrealized gains (losses) on investment securities	17		4		76		150
Foreign currency translation adjustment	4		(1)		7		4
Pension and other postretirement benefit adjustments	7		16		20		35
Other	1		(1)		1		(1)
Total other comprehensive income (loss)	26		(41)		93		319
Comprehensive Income (Loss) Attributable to MUAH	258		219		849		975
Comprehensive loss from noncontrolling interests	(10)		(39)		(25)		(62)
Total Comprehensive Income (Loss)	$ 248		$ 180		$ 824		$ 913

[1] The transferred IHC entities are not measured using a "market view" perspective.

[2] The transferred IHC entities are not measured using a "market view" perspective.

[3] The transferred IHC entities are not measured using a "market view" perspective.

[4] The transferred IHC entities are not measured using a "market view" perspective.