Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	$ 1,000,000		$ 1,000,000
Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	34,000,000		37,000,000
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	115,000,000		116,000,000
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	4,500,000,000		4,600,000,000
Liabilities related to consolidated VIEs	4,300,000,000		4,600,000,000
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	178,000,000	167,000,000
Expense related to investments	164,000,000	212,000,000
Expenses related to investments recognized in tax expense	71,000,000	80,000,000
Investment tax credits	103,000,000	69,000,000
Assets related to consolidated VIEs	2,500,000,000		2,500,000,000
Liabilities related to consolidated VIEs	1,900,000,000		1,800,000,000
Investment carrying amount	4,036,000,000		4,178,000,000
Maximum exposure to loss	7,453,000,000		7,390,000,000
Private Investment Funds And Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	99,000,000		98,000,000
Maximum exposure to loss	$ 107,000,000		$ 107,000,000