Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Variable Interest Entity [Line Items]
Tax credits related to tax-advantaged investments		$ 141	$ 148	$ 424	$ 435
Investment tax credits		133	238	311	474
Expense related to tax-advantaged investments		135	$ 134	418	$ 399
Investments in VIEs		686,469		686,469		$ 663,491
Available-for-sale securities	[1]	81,704		81,704		69,706
Liabilities related to VIEs		627,148		627,148		607,720
Variable Interest Entity Not Primary Beneficiary | Minimum
Variable Interest Entity [Line Items]
Net investments in unconsolidated VIEs		1		1		1
Variable Interest Entity Not Primary Beneficiary | Maximum
Variable Interest Entity [Line Items]
Net investments in unconsolidated VIEs		79		79		86
Variable Interest Entity, Not Primary Beneficiary, Private Investment Funds and Partnerships
Variable Interest Entity [Line Items]
Investments in VIEs		257		257		219
Maximum exposure to loss		382		382		319
Variable Interest Entity, Not Primary Beneficiary, Securitization Vehicles | Senior Notes
Variable Interest Entity [Line Items]
Available-for-sale securities		3,700		3,700		5,300
Collateral held related to senior notes		4,200		4,200		6,100
Variable Interest Entity, Primary Beneficiary, Community Development and Tax-Advantaged Investments
Variable Interest Entity [Line Items]
Investments in VIEs		5,800		5,800		6,100
Liabilities related to VIEs		3,800		3,800		4,400
Variable Interest Entity, Primary Beneficiary, Tender Option Bond Program
Variable Interest Entity [Line Items]
Investments in VIEs		228		228		607
Liabilities related to VIEs		$ 150		$ 150		$ 381

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.