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
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

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

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