Credit Loss Reserves - Summarizes Changes in Credit Loss Reserves by Product/Class and Related Receivable Balance by Product - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Write-offs	$ 147	[1]	$ 311	[1]
Excludes Credit loss reserves for TDR Loans that are carried at the lower of amortized cost or fair value	22		39
Real Estate Secured Receivable Portfolio [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Write-offs	15		20
TDR [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Excludes TDR loans that are carried at the lower of amortized cost or fair value	399		637
Mortgage Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Release of provision associated with a correction to the reserve calculation for a segment of the portfolio	$ 19

[1] For collateral dependent receivables that are transferred to held for sale, existing credit loss reserves at the time of transfer are recognized as a charge-off. We transferred to held for sale certain real estate secured receivables during the three months ended March 31, 2015 and 2014 that were carried at the lower of amortized cost or fair value of the collateral less cost to sell. Accordingly, we recognized the existing credit loss reserves on these receivables as additional charge-off totaling $15 million and $20 million during the three months ended March 31, 2015 and 2014, respectively.