Goodwill and Other Intangible Assets - Summary of the Key Characteristics, Inputs, and Economic Assumptions Used to Estimate the Fair Value of the Company's MSRs (Detail) (Estimate of Fair Value, Fair Value Disclosure, USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Estimate of Fair Value, Fair Value Disclosure
Fair value of retained MSRs	$ 831	$ 921
Prepayment rate assumption (annual)	19.00%	20.00%
Decline in fair value from 10% adverse change	49	52
Decline in fair value from 20% adverse change	92	98
Discount rate (annual)	11.00%	11.00%
Decline in fair value from 10% adverse change	31	33
Decline in fair value from 20% adverse change	$ 60	$ 63
Weighted-average life (in years)	4 years 3 months	4 years 3 months
Weighted-average coupon	4.90%	5.20%

Goodwill and Other Intangible Assets - Summary of the Key Characteristics, Inputs, and Economic Assumptions Used to Estimate the Fair Value of the Company's MSRs (Detail) (Estimate of Fair Value, Fair Value Disclosure, USD $)
In Millions, unless otherwise specified

9 Months Ended

12 Months Ended

Sep. 30, 2012

Dec. 31, 2011

Estimate of Fair Value, Fair Value Disclosure

Fair value of retained MSRs

$ 831

$ 921

Prepayment rate assumption (annual)

19.00%

20.00%

Decline in fair value from 10% adverse change

Decline in fair value from 20% adverse change

Discount rate (annual)

11.00%

Decline in fair value from 10% adverse change

Decline in fair value from 20% adverse change

$ 60

$ 63

Weighted-average life (in years)

4 years 3 months

Weighted-average coupon

4.90%

5.20%

- Definition

Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

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- Definition

Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred.

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- Definition

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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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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- Definition

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References+ Details

- Definition

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References+ Details