Credit Loss Reserves - Analysis of Credit Loss Reserves (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses related to the lower of amortized cost or fair value attributable to credit for personal non-credit card receivables	$ 112
Personal non-credit card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses related to the lower of amortized cost or fair value attributable to credit for personal non-credit card receivables	$ 112