Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Jun. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Collateral from counterparties to offset changes in the fair value of derivative assets	$ 989	$ 1,100	$ 1,200
Valuation adjustments related to the credit risk associated with counterparties of customer accommodation derivative contracts	30	23	28
Collateral from counterparties to offset changes in the fair value of derivative liabilities	646	927	788
Cash Flow Hedging
Derivative [Line Items]
Maximum length of time hedged in cash flow hedge		44 months
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	68	69	80
Net deferred gains, net of tax, recorded in accumulated other comprehensive income are expected to be reclassified into earnings		56
Interest Rate Contract | Lender Concentration Risk
Derivative [Line Items]
Notional amount of the risk participation agreements	723	957	808
Credit Risk Derivatives Average Life		2.8
Interest Rate Contract | Lender Concentration Risk | Servicing Contracts
Derivative [Line Items]
Fair value of risk participation agreements	$ 2	$ 2	$ 2