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Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2013 | Dec. 31, 2012
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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 | $ 1,667,651 | $ 1,782,999
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 | 4,372,613 | 4,707,454
AFS [Member] | Interest rate swaps [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 704,272 | 727,926
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 | 1,576,832 | 1,657,382
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 | 161,690
AFS [Member] | Futures contracts [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | 161,500 | 161,500
AFS [Member] | Other contracts [Member] |  |
Schedule Of Notional Amounts Of Parents Financial Services Trading Derivative Products [Line Items] |  |
Derivative products, Notional Amount | $ 75,651 | $ 75,651

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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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