Mortgage Loans Held for Sale and Investment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Mortgage Loans Held for Sale and Investment [Abstract]
Mortgage loans held for sale in foreclosure	$ 24		$ 21
Sale of mortgage loans held for sale	13,724	$ 6,194
Gain on sale of mortgage loans held for sale	$ 275	$ 106

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=118932676&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=118932676&loc=d3e3536-108585

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