Mortgage Loans Held for Sale - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Mortgage Loans Held for Sale and Investment [Abstract]
Sale of mortgage loans held for sale	$ 43,040	$ 27,778
Gain on sale of mortgage loans held for sale	855	$ 365
Mortgage loans held for sale in foreclosure	$ 20		$ 21

The cash inflow from sales of loans that are secured with real estate mortgages and are held with the intention to resell in the near future.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3461-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration