Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Derivative [Line Items]
Collateral from counterparties to offset changes in the fair value of derivative assets	$ 1,200	$ 1,200	$ 1,100	$ 903
Valuation adjustments related to the credit risk associated with counterparties of customer accommodation derivative contracts		33	51	41
Collateral from counterparties to offset changes in the fair value of derivative liabilities	758	758	943	680
Reclassified gains (losses) from accumulated other comprehensive income into earnings as the original forecasted transaction was no longer probable of occurring within the originally specified time period	11
Interest Rate Floor | Cash Flow Hedging
Derivative [Line Items]
Deferred gains, net of tax, on cash flow hedges were recorded in accumulated other comprehensive income	92	92	74	67
Net deferred gains, net of tax, recorded in accumulated other comprehensive income are expected to be reclassified into earnings	61	61
Interest Rate Contract | Lender Concentration Risk
Derivative [Line Items]
Notional amount of the risk participation agreements	722	722	776	851
Credit Risk Derivatives Average Life	2.6	2.6
Interest Rate Contract | Lender Concentration Risk | Servicing Contracts
Derivative [Line Items]
Fair value of risk participation agreements	$ 2	$ 2	$ 1	$ 1