Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
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	45,000,000		46,000,000
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds	17,000,000	$ 30,000,000
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	168,000,000	168,000,000
Expense related to investments	151,000,000	146,000,000
Investment tax credits	223,000,000	114,000,000
Expenses related to investments recognized in tax expense	67,000,000	$ 66,000,000
Investment carrying amount	5,370,000,000		5,257,000,000
Maximum exposure to loss	9,551,000,000		9,436,000,000
Assets related to consolidated VIEs	2,900,000,000		3,000,000,000
Liabilities related to consolidated VIEs	2,200,000,000		2,200,000,000
Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	28,000,000		32,000,000
Maximum exposure to loss	44,000,000		47,000,000
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	28,000,000		28,000,000
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	2,000,000,000		2,300,000,000
Liabilities related to consolidated VIEs	$ 2,000,000,000		$ 2,200,000,000