Goodwill and Mortgage Servicing Rights - by Business Segment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Total goodwill	$ 49,248		$ 47,823	$ 47,471	$ 47,507
Consumer & Community Banking
Goodwill [Line Items]
Total goodwill	31,311		30,133	30,084
Consumer & Community Banking | Revisions
Goodwill [Line Items]
Total goodwill	51	$ (959)
Corporate & Investment Bank
Goodwill [Line Items]
Total goodwill	7,913		7,901	7,721
Corporate & Investment Bank | Revisions
Goodwill [Line Items]
Total goodwill		$ 959
Commercial Banking
Goodwill [Line Items]
Total goodwill	2,985		2,982	2,860
Asset & Wealth Management
Goodwill [Line Items]
Total goodwill	7,039		$ 6,807	$ 6,806
Asset & Wealth Management | Revisions
Goodwill [Line Items]
Total goodwill	$ (51)