Federal Funds Sold and Securities Borrowed or Purchased Under Agreements to Resell - Additional Information (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets Sold under Agreements to Repurchase [Line Items]
Collateral Requirements Minimum Percentage Collateral To Fair Value Of Securities Purchased Under Repurchase Agreements	95.00%
Collateral Requirements Maximum Percentage Collateral To Fair Value Of Securities Purchased Under Repurchase Agreements	110.00%
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	$ 1,100	$ 913
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	211	234
Amount of Repurchase Agreements Secured by Trading Assets	992	717
Repurchase Agreements [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Trading Securities Pledged as Collateral	$ 1,000	$ 731

Amount of Repurchase Agreements Secured by Trading Assets

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- Definition

Collateral Requirements Maximum Percentage Collateral To Fair Value Of Securities Purchased or Borrowed Under Repurchase Agreements

+ References

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- Definition

Collateral Requirements, Minimum Percentage, Collateral To Fair Value Of Securities Purchased or Borrowed Under Repurchase Agreements

+ References

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- Definition

Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

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- Definition

Fair value of the collateral, or portion thereof, that has been re-pledged, delivered, or otherwise used.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

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- Definition

The fair value of trading securities that serve as collateral for borrowings.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524

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