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, 2021	Dec. 31, 2020
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 1,266,530	$ 1,165,688
Total carrying value	2,841	2,753
Standby letters of credit and other financial guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	19,823	22,850
Noninvestment-grade	8,120	8,132
Total lending-related commitments	27,943	30,982
Allowance for lending-related commitments	78	80
Guarantee liability	536	363
Total carrying value	614	443
Commitments with collateral	15,071	17,238
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	3,502	2,263
Noninvestment-grade	899	790
Total lending-related commitments	4,401	3,053
Allowance for lending-related commitments	10	14
Guarantee liability	0	0
Total carrying value	10	14
Commitments with collateral	$ 929	$ 498