Commitments and Contingencies (Details) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012 USD ($)	Mar. 31, 2012 GBP (£)	Mar. 31, 2012 Alleged Damages - Minimum USD ($)	Mar. 31, 2012 Alleged Damages - Maximum USD ($)
Loss Contingencies [Line Items]
Portfolio amount of client seeking damages (in pounds)		£ 500
Damages sought			177	234
Realized losses in the portfolio	$ 125

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details