Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
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	60,000,000		40,000,000
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds	6,000,000	$ 17,000,000
Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	29,000,000		28,000,000
Maximum exposure to loss	49,000,000		50,000,000
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	161,000,000	168,000,000
Expense related to investments	145,000,000	151,000,000
Investment tax credits	259,000,000	223,000,000
Expenses related to investments recognized in tax expense	63,000,000	$ 67,000,000
Investment carrying amount	5,025,000,000		5,009,000,000
Maximum exposure to loss	10,641,000,000		10,373,000,000
Assets related to consolidated VIEs	3,400,000,000		3,500,000,000
Liabilities related to consolidated VIEs	2,500,000,000		2,600,000,000
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	23,000,000		24,000,000
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	1,500,000,000		1,100,000,000
Liabilities related to consolidated VIEs	$ 1,500,000,000		$ 1,100,000,000