Net Gains (Losses) Relating to Derivative Instruments Designated as Cash Flow Hedges (Detail) (Cash Flow Hedging, USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pretax net (losses) gains recognized in OCI	$ 52	$ 15
Interest Income (Expense) Net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pretax net gains reclassified from OCI into net income	$ 16	$ 10

Amount before tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e689-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph c

-URI http://asc.fasb.org/extlink&oid=35706170&loc=d3e41638-113959

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