Mortgage Loans Held for Sale - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Mortgage Loans Held for Sale and Investment [Abstract]
Mortgage loans held for sale in foreclosure	$ 21		$ 21
Sale of mortgage loans held for sale	26,606	$ 15,422
Gain on sale of mortgage loans held for sale	$ 457	$ 219

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

Name:	us-gaap_ProceedsFromSaleOfMortgageLoansHeldForSale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration