Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	$ 1		$ 1		$ 1
Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	93		93		95
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds	7	$ 6	14	$ 12
Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	31		31		27
Maximum exposure to loss	53		53		52
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	146	170	291	336
Expense related to investments	137	155	269	301
Investment tax credits	162	141	246	278
Expenses related to investments recognized in tax expense	76	$ 68	157	$ 135
Investment carrying amount	5,839		5,839		5,823
Maximum exposure to loss	12,540		12,540		12,360
Assets related to consolidated VIEs	3,700		3,700		3,900
Liabilities related to consolidated VIEs	2,900		2,900		2,700
Conduit [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	14		14		14
Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	2,600		2,600		2,400
Liabilities related to consolidated VIEs	$ 2,300		$ 2,300		$ 2,300