Sensitivity of the Current Fair Value of Residual Cash Flows to Immediate 10%, 20% and 50% Adverse Changes in Assumptions (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
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	$ 898	[1]
Weighted- Average Life (in years)	6 years 4 months 24 days	[1]
Prepayment Speed (annual)	10.80%	[1]
Impact of Adverse Change on Fair Value 10%	(38)	[1]
Impact of Adverse Change on Fair Value 20%	(73)	[1]
Impact of Adverse Change on Fair Value 50%	(164)	[1]
Discount Rate (annual)	9.90%	[1]
Impact of Adverse Change on Fair Value 10%	(33)	[1]
Impact of Adverse Change on Fair Value 20%	(65)	[1]
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	35	[1]
Weighted- Average Life (in years)	3 years 1 month 6 days	[1]
Prepayment Speed (annual)	26.00%	[1]
Impact of Adverse Change on Fair Value 10%	(1)	[1]
Impact of Adverse Change on Fair Value 20%	(2)	[1]
Impact of Adverse Change on Fair Value 50%	(5)	[1]
Discount Rate (annual)	11.80%	[1]
Impact of Adverse Change on Fair Value 10%	(1)	[1]
Impact of Adverse Change on Fair Value 20%	$ (2)	[1]

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