Business Segments - Impacts of Changes to Internal Management Reporting (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		$ (929)	$ 356	$ 729
Total Assets		229,677	214,223	203,375
Group Reporting Basis Total deposits		137,037	103,589	97,371
Group Reporting Basis Goodwill		358	1,051	1,260
Out of period pension adjustment				10
Operating Segments [Member] | WPB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(1,187)	(412)	(47)
Total Assets		59,200	50,851	53,298
Group Reporting Basis Total deposits		50,000	44,553	41,806
Group Reporting Basis Goodwill		0	693	902
Operating Segments [Member] | CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		175	432	502
Total Assets		36,354	34,241	34,214
Group Reporting Basis Total deposits		42,369	29,986	23,938
Group Reporting Basis Goodwill		358	358	358
Operating Segments [Member] | GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		387	571	834
Total Assets		132,363	126,710	112,911
Group Reporting Basis Total deposits		44,668	29,050	31,627
Group Reporting Basis Goodwill		0	0	0
Operating Segments [Member] | CC [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(304)	(235)	(560)
Total Assets		1,760	2,421	2,952
Group Reporting Basis Total deposits		0	0	0
Group Reporting Basis Goodwill		$ 0	0	0
As Previously Reported [Member] | Operating Segments [Member] | RBWM [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			(465)	(138)
Total Assets	[1]		19,429	19,000
Group Reporting Basis Total deposits			37,009	32,612
Group Reporting Basis Goodwill			372	581
As Previously Reported [Member] | Operating Segments [Member] | CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			410	477
Total Assets			25,737	25,047
Group Reporting Basis Total deposits			29,632	23,604
As Previously Reported [Member] | Operating Segments [Member] | GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			472	721
Total Assets			88,440	73,187
Group Reporting Basis Total deposits			27,605	30,181
As Previously Reported [Member] | Operating Segments [Member] | PB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			(9)	13
Total Assets	[1]		7,326	6,797
Group Reporting Basis Total deposits			6,539	8,193
Group Reporting Basis Goodwill			321	321
As Previously Reported [Member] | Operating Segments [Member] | CC [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			(52)	(344)
Total Assets			73,291	79,344
Group Reporting Basis Total deposits			$ 2,804	$ 2,781

[1] Segment total assets included goodwill that was previously allocated to RBWM and PB of $372 million and $321 million, respectively, at December 31, 2019 and $581 million and $321 million, respectively, at December 31, 2018.