Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) (USD $)	3 Months Ended			1 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	May 01, 2013 Scenario, Forecast [Member]
Variable Interest Entity [Line Items]
Realized federal and state income tax credits on investments	$ 236,000,000	$ 166,000,000
Amortization expense recorded in tax expense on tax-advantaged investments	149,000,000	89,000,000
Amortization expense recognized in other noninterest expense on tax-advantaged investments	132,000,000	101,000,000
Assets related to community development and tax-advantaged investment entities VIEs	7,200,000,000		7,100,000,000
Liabilities related to community development and tax-advantaged investment entities VIEs	5,200,000,000		5,200,000,000
Decrease in other assets as a result of deconsolidation of VIEs				4,000,000,000
Decrease in long-term debt as a result of deconsolidation of VIEs				4,000,000,000
Held-to-maturity investment securities related to the conduit, in balance sheet	139,000,000		144,000,000
Available-for-sale securities related to the tender option bond program	5,200,000,000		5,300,000,000
Short-term borrowings related to tender option bond program	4,900,000,000		5,000,000,000
Investment in an unconsolidated VIE of bottom of range	1,000,000		1,000,000
Investment in an unconsolidated VIE of top of range	51,000,000		58,000,000
Aggregate amount of investments in unconsolidated VIEs	1,900,000,000		1,900,000,000
Unfunded capital commitments related to unconsolidated VIEs	1,300,000,000		1,300,000,000
Company's maximum exposure to unconsolidated VIEs, including any tax implications	5,200,000,000		5,200,000,000
Company's maximum exposure to loss related to community development tax-advantaged investments	1,800,000,000		1,800,000,000
Company's maximum exposure previously recorded tax credits	$ 3,300,000,000		$ 3,300,000,000