Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	$ 1,000,000		$ 81,000,000
Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	1,000,000		95,000,000
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds	7,000,000	$ 6,000,000
Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	30,000,000		27,000,000
Maximum exposure to loss	52,000,000		52,000,000
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	145,000,000	166,000,000
Expense related to investments	132,000,000	146,000,000
Investment tax credits	84,000,000	137,000,000
Expenses related to investments recognized in tax expense	81,000,000	$ 67,000,000
Investment carrying amount	5,836,000,000		5,823,000,000
Maximum exposure to loss	12,398,000,000		12,360,000,000
Assets related to consolidated VIEs	3,700,000,000		3,900,000,000
Liabilities related to consolidated VIEs	2,900,000,000		2,700,000,000
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	14,000,000		14,000,000
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	2,500,000,000		2,400,000,000
Liabilities related to consolidated VIEs	$ 2,300,000,000		$ 2,300,000,000