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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	$ 546,652		$ 546,652		$ 495,426
Liabilities related to consolidated VIEs	494,172		494,172		442,943
Community Development And Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense	145	$ 146	295	$ 291
Expense related to investments	145	137	287	269
Investment tax credits	90	162	189	246
Expenses related to investments recognized in tax expense	99	76	200	157
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds	13	$ 7	21	$ 14
Variable Interest Entity Not Primary Beneficiary [Member] | Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss	55		55		55
Assets related to consolidated VIEs	34		34		31
Variable Interest Entity Not Primary Beneficiary [Member] | Community Development And Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss	12,204		12,204		12,118
Assets related to consolidated VIEs	6,345		6,345		6,148
Liabilities related to consolidated VIEs	2,966		2,966		2,938
Variable Interest Entity Not Primary Beneficiary [Member] | Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	1		1		1
Variable Interest Entity Not Primary Beneficiary [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs	84		84		87
Variable Interest Entity Primary Beneficiary [Member] | Community Development And Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	3,700		3,700		4,000
Liabilities related to consolidated VIEs	2,900		2,900		3,200
Variable Interest Entity Primary Beneficiary [Member] | Tender Option Bond Program [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs	3,000		3,000		3,000
Liabilities related to consolidated VIEs	$ 1,500		$ 1,500		$ 2,700