Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Variable Interest Entity [Line Items]
Realized federal and state income tax credits on investments	$ 304,000,000	$ 188,000,000	$ 540,000,000	$ 354,000,000
Amortization expense recorded in tax expense on tax-advantaged investments	231,000,000	104,000,000	380,000,000	193,000,000
Amortization expense recognized in other noninterest expense on tax-advantaged investments	127,000,000	120,000,000	259,000,000	221,000,000
Decrease in other asset as a result of deconsolidation of VIE'S	4,600,000,000
Decrease in long-term debt as a result of deconsolidation of VIE'S	4,600,000,000
Company's investment in unconsolidated VIEs	1,100,000,000		1,100,000,000
Aggregate amount of investments in unconsolidated VIEs	2,600,000,000		2,600,000,000		1,900,000,000
Unfunded capital commitments related to unconsolidated VIEs	1,800,000,000		1,800,000,000		1,300,000,000
Company's maximum exposure to unconsolidated VIEs, including any tax implications	6,800,000,000		6,800,000,000		5,200,000,000
Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	1,000,000		1,000,000		1,000,000
Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	44,000,000		44,000,000		58,000,000
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	1,700,000,000		1,700,000,000		7,100,000,000
Liabilities related to consolidated VIEs	462,000,000		462,000,000		5,200,000,000
Aggregate amount of investments in unconsolidated VIEs	2,500,000,000		2,500,000,000		1,800,000,000
Company's maximum exposure previously recorded tax credits	4,200,000,000		4,200,000,000		3,300,000,000
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	4,900,000,000		4,900,000,000		5,300,000,000
Liabilities related to consolidated VIEs	4,800,000,000		4,800,000,000		5,000,000,000
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	$ 136,000,000		$ 136,000,000		$ 144,000,000