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Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
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Interest rate swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | $ 1,782,999 | $ 1,702,113
Interest rate swaps-pay-fixed/receive variable [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 4,707,454 | 4,535,626
Currency swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 755,438 | 721,168
AFS [Member] | Interest rate swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 727,926 | 1,370,995
AFS [Member] | Interest rate swaps-pay-fixed/receive variable [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 1,657,382 | 3,798,305
AFS [Member] | Interest rate swaps-basis swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 161,690 | 175,835
AFS [Member] | Currency swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount |  | 13,559
AFS [Member] | Future contracts [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 161,500 | 53,500
AFS [Member] | Other contracts [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | $ 75,651 | $ 118,930

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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