Securities Available for Sale and Securities Held to Maturity - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2011 CreditScore Location		Sep. 30, 2010		Sep. 30, 2011 CreditScore Location		Sep. 30, 2010		Dec. 31, 2010	Dec. 31, 2009
Gain (Loss) on Investments [Line Items]
Securities available for sale Gross Unrealized Losses	$ 236				$ 236				$ 240
Fair Isaac & Company minimum credit score for Prime loan origination	620				620
Cash and cash equivalents	6,376		5,701		6,376		5,701		4,931	8,241
Loan-to-deposit ratio	18.00%				18.00%
Net impairment losses on securities	13	[1]	3	[1]	22	[1]	19	[1]
Securities available for sale Amortized Cost	28,872				28,872				23,967
Securities available for sale	28,962				28,962				23,993
Alt-A residential mortgage backed securities
Gain (Loss) on Investments [Line Items]
Securities available for sale Amortized Cost	412				412
Securities available for sale	$ 305				$ 305

[1] Net impairment losses on securities include total other-than-temporary impairment losses of $2 million and $0 million, net of $(11) million and $(3) million recognized in other comprehensive income, for the three months ended September 30, 2011 and 2010, respectively, and total other-than-temporary impairment losses of $13 million and $41 million, net of $(9) million and $22 million recognized in other comprehensive income, for the nine months ended September 30, 2011 and 2010, respectively.