Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net (Loss) Income Attributable to MUAH	$ (306)	$ 184
Other Comprehensive Income (Loss), Net of Tax:
Net change in unrealized gains (losses) on cash flow hedges	326	24
Net change in unrealized gains (losses) on investment securities	258	152
Pension and other postretirement benefit adjustments	16	6
Other	0	1
Total other comprehensive income (loss)	600	183
Comprehensive Income (Loss) Attributable to MUAH	294	367
Comprehensive income (loss) from noncontrolling interests	(4)	(5)
Total Comprehensive Income (Loss)	$ 290	$ 362