Derivatives and Hedging Activities - Fair Value of Credit Derivatives Purchased and Sold (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Maximum [Member] \| Other [Member]
Credit Derivatives [Line Items]
Fair value of other credit derivatives sold	$ 1	$ 1	$ 1

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CreditDerivativesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration