Credit Quality - Summary of the Credit Risk Profile of the Residential Mortgage and Consumer Portfolio Segments by Class (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Residential Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans measured at fair value on a recurring basis	$ 184	$ 179

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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