Variable Interest Entities - Schedule of Options to Repurchase Delinquent Loans (Details) - Nonconsolidated entities - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Loans repurchased or option to repurchase	$ 7,207	$ 8,629
Real estate acquired through foreclosure	78	95
Residential mortgage
Variable Interest Entity [Line Items]
Real estate acquired through foreclosure	$ 404	$ 527

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5162-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4437-111522

Name:	us-gaap_RealEstateAcquiredThroughForeclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant