Goodwill and Mortgage Servicing Rights (Goodwill by Business Segment 10-K) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill	$ 9,233	$ 9,218	$ 9,173
Retail Banking
Goodwill [Line Items]
Goodwill	5,795	5,795	5,795
Corporate & Institutional Banking
Goodwill [Line Items]
Goodwill	3,374	3,359	3,314
Goodwill from business acquisitions	15	45
Asset Management Group
Goodwill [Line Items]
Goodwill	$ 64	$ 64	$ 64

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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