Guarantees and Contingent Liabilities - Summary of Other Guarantees and Contingent Liabilities (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Collateral Held	$ 0
Carrying Amount	22
Maximum Potential Future Payments	10,707
Third Party Borrowing Arrangements [Member]
Guarantor Obligations [Line Items]
Collateral Held	0
Carrying Amount	0
Maximum Potential Future Payments	11
Securities Lending Indemnifications [Member]
Guarantor Obligations [Line Items]
Collateral Held	8,360
Carrying Amount	0
Maximum Potential Future Payments	8,123
Asset Sales [Member]
Guarantor Obligations [Line Items]
Collateral Held	0
Carrying Amount	99
Maximum Potential Future Payments	8,631
Merchant Processing [Member]
Guarantor Obligations [Line Items]
Collateral Held	883
Carrying Amount	82
Maximum Potential Future Payments	148,691
Tender Option Bond Program Guarantee [Member]
Guarantor Obligations [Line Items]
Collateral Held	941
Carrying Amount	0
Maximum Potential Future Payments	997
Other Guarantees [Member]
Guarantor Obligations [Line Items]
Collateral Held	0
Carrying Amount	21
Maximum Potential Future Payments	$ 1,947