Business Segments - Impacts of Changes to Internal Management Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense	$ 325	$ (998)
Total Assets	219,949	269,609
Group Reporting Basis Total deposits	141,139	124,315
WPB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense	11	(869)
Total Assets	63,747	58,246
Group Reporting Basis Total deposits	49,578	48,800
CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense	144	(2)
Total Assets	44,170	42,882
Group Reporting Basis Total deposits	42,874	32,844
GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense	191	45
Total Assets	110,524	165,838
Group Reporting Basis Total deposits	48,687	42,671
CC [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense	(21)	(172)
Total Assets	1,508	2,643
Group Reporting Basis Total deposits	$ 0	0
As Previously Reported [Member] | RBWM [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(546)
Total Assets		18,954
Group Reporting Basis Total deposits		39,083
As Previously Reported [Member] | CMB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(3)
Total Assets		31,540
Group Reporting Basis Total deposits		32,309
As Previously Reported [Member] | GB&M [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		43
Total Assets		114,802
Group Reporting Basis Total deposits		40,417
As Previously Reported [Member] | PB [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(323)
Total Assets		7,159
Group Reporting Basis Total deposits		8,201
As Previously Reported [Member] | CC [Member]
Segment Reporting Information [Line Items]
Profit (Loss) before Income Tax Expense		(169)
Total Assets		97,154
Group Reporting Basis Total deposits		$ 4,305