Payment Status for the LHFI Portfolio (Additional Information) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Loans Receivable, Fair Value Disclosure	$ 196	$ 222
Nonaccruing 90 Plus Days Past Due	357	360
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Loans Receivable, Fair Value Disclosure	$ 196	$ 222

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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