Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Variable Interest Entity [Line Items]
Realized federal and state income tax credits on investments	$ 227,000,000	$ 191,000,000	$ 581,000,000	$ 510,000,000
Amortization expense recorded in tax expense on tax-advantaged investments	123,000,000	60,000,000	316,000,000	175,000,000
Amortization expense recognized in other noninterest expense on tax-advantaged investments	140,000,000	144,000,000	361,000,000	386,000,000
Assets related to community development and tax-advantaged investment entities VIEs	6,700,000,000		6,700,000,000		5,600,000,000
Liabilities related to community development and tax-advantaged investment entities VIEs	4,800,000,000		4,800,000,000		4,000,000,000
Held-to-maturity investment securities related to the conduit, in balance sheet	151,000,000		151,000,000		202,000,000
Available-for-sale securities related to the tender option bond program	5,300,000,000		5,300,000,000		5,400,000,000
Short-term borrowings related to tender option bond program	5,000,000,000		5,000,000,000		5,300,000,000
Investment in an unconsolidated VIE of bottom of range	1,000,000		1,000,000		1,000,000
Investment in an unconsolidated VIE of top of range	44,000,000		44,000,000		37,000,000
Aggregate amount of investments in unconsolidated VIEs	1,700,000,000		1,700,000,000		1,800,000,000
Unfunded capital commitments related to unconsolidated VIEs	1,100,000,000		1,100,000,000		965,000,000
Company's maximum exposure to unconsolidated VIEs, including any tax implications	5,000,000,000		5,000,000,000		4,800,000,000
Company's maximum exposure to loss related to community development tax-advantaged investments	1,700,000,000		1,700,000,000		1,800,000,000
Company's maximum exposure previously recorded tax credits	$ 3,200,000,000		$ 3,200,000,000		$ 3,000,000,000