Sensitivity of the Current Fair Value of Residual Cash Flows to Immediate 10%, 20% and 50% Adverse Changes in Assumptions (Detail) (USD $)	Jun. 30, 2012
Fixed Rate Residential Mortgage
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair Value	$ 702,000,000	[1]
Weighted- Average Life (in years)	5.1
Rate	15.20%
Impact of Adverse Change on Fair Value 10%	(36,000,000)
Impact of Adverse Change on Fair Value 20%	(69,000,000)
Impact of Adverse Change on Fair Value 50%	(155,000,000)
Discount Rate	10.60%
Impact of Adverse Change on Fair Value 10%	(24,000,000)
Impact of Adverse Change on Fair Value 20%	(47,000,000)
Adjustable Rate Residential Mortgage
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair Value	34,000,000	[1]
Weighted- Average Life (in years)	3.1
Rate	27.10%
Impact of Adverse Change on Fair Value 10%	(2,000,000)
Impact of Adverse Change on Fair Value 20%	(3,000,000)
Impact of Adverse Change on Fair Value 50%	(7,000,000)
Discount Rate	11.70%
Impact of Adverse Change on Fair Value 10%	(1,000,000)
Impact of Adverse Change on Fair Value 20%	$ (2,000,000)

[1] (a) The impact of the weighted-average default rate on the current fair value of residual cash flows for all scenarios is immaterial.