Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Oct. 01, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Borrowings, fair values	$ 14,700	$ 14,200
Outstanding principal amount for sold mortgage receivables	220
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of residual interest	$ 35	$ 40
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit support for outstanding balance of sold mortgage receivables	70.00%

The total principal outstanding of financial assets transferred in a securitization, asset-backed financing arrangement, or similar transfer that has been accounted for as sales and in which the transferor continues to have involvement, including both the derecognized and recognized portion of such transferred assets.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the interests continued to be held by a transferor (retained or residual interest) after transferring financial assets to a third party.

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