Business Segments - Impacts of Changes to Internal Management Reporting (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		$ (121)	$ (33)	$ (1,072)	$ 360
Total Assets		232,867	222,515	232,867	222,515
Group Reporting Basis Total deposits		139,779	103,964	139,779	103,964
Group Reporting Basis Goodwill		358	1,051	358	1,051
Operating Segments [Member] | WPB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(229)	(257)	(1,164)	(291)
Total Assets		56,728	52,334	56,728	52,334
Group Reporting Basis Total deposits		48,477	43,974	48,477	43,974
Group Reporting Basis Goodwill		0	693	0	693
Operating Segments [Member] | CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		139	118	70	354
Total Assets		38,096	36,968	38,096	36,968
Group Reporting Basis Total deposits		39,736	25,975	39,736	25,975
Group Reporting Basis Goodwill		358	358	358	358
Operating Segments [Member] | GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		64	157	274	452
Total Assets		136,478	130,708	136,478	130,708
Group Reporting Basis Total deposits		51,566	34,015	51,566	34,015
Group Reporting Basis Goodwill		0	0	0	0
Operating Segments [Member] | CC [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(95)	(51)	(252)	(155)
Total Assets		1,565	2,505	1,565	2,505
Group Reporting Basis Total deposits		0	0	0	0
Group Reporting Basis Goodwill		$ 0	0	$ 0	0
As Previously Reported [Member] | Operating Segments [Member] | RBWM [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			(275)		(347)
Total Assets	[1]		19,128		19,128
Group Reporting Basis Total deposits			34,877		34,877
Group Reporting Basis Goodwill			372		372
As Previously Reported [Member] | Operating Segments [Member] | CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			111		332
Total Assets			27,734		27,734
Group Reporting Basis Total deposits			25,489		25,489
As Previously Reported [Member] | Operating Segments [Member] | GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			124		355
Total Assets			89,154		89,154
Group Reporting Basis Total deposits			32,002		32,002
As Previously Reported [Member] | Operating Segments [Member] | PB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense			0		(3)
Total Assets	[1]		7,042		7,042
Group Reporting Basis Total deposits			7,720		7,720
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			7		23
Total Assets			79,457		79,457
Group Reporting Basis Total deposits			$ 3,876		$ 3,876

[1] Segment total assets at September 30, 2019 included goodwill that was previously allocated to RBWM and PB of $372 million and $321 million, respectively.