MSR (Sales of Receivables and Servicing Rights - Additional Information) (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Disclosure - Activity Related to Mortgage Banking Net Revenue [Abstract]
Sevicing of residential mortgage loans for other investors			$ 60,800	$ 53,600
Amortization	$ (35)	$ (96)

Amount of amortization of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746

Name:	us-gaap_ServicingAssetAtAmortizedValueAmortization1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration