Trading Assets and Liabilities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	$ 25,156	$ 28,894
Collateralized Mortgage Backed Securities [Member] \| Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	88	133
Collateralized Mortgage Backed Securities [Member] \| Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	$ 27	$ 26

Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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