Derivatives and Hedging Activities - Gain (Loss) from Interest Rate Hedges and Related Hedged Borrowings and Deposits (Parenthetical) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Derivative Contracts Accounted for as Hedges [Member]
Derivative [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ (684)

Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109977999&loc=d3e76258-113986

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration