Off-balance Sheet Lending-related Financial Instruments, Guarantees, and Other Commitments - Standby Letters of Credit and Other Financial Guarantees (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 1,576,476	$ 1,497,847
Allowance for lending-related commitments	2,142	1,974	$ 2,075	$ 2,382
Total carrying value	3,835	4,139
Standby letters of credit and other financial guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	20,602	19,694
Noninvestment-grade	8,623	9,178
Total lending-related commitments	29,225	28,872
Allowance for lending-related commitments	102	110
Guarantee liability	382	369
Total carrying value	484	479
Commitments with collateral	16,305	16,861
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	3,128	3,552
Noninvestment-grade	910	836
Total lending-related commitments	4,038	4,388
Allowance for lending-related commitments	38	37
Guarantee liability	0	0
Total carrying value	38	37
Commitments with collateral	$ 384	$ 539