Off-balance Sheet Lending-related Financial Instruments, Guarantees, and Other Commitments - Standby Letters of Credit and Other Financial Guarantees (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 1,242,022	$ 1,165,688
Total carrying value	3,570	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	26,955	22,850
Noninvestment-grade	7,921	8,132
Total lending-related commitments	34,876	30,982
Allowance for lending-related commitments	67	80
Guarantee liability	596	363
Total carrying value	663	443
Commitments with collateral	21,401	17,238
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	3,072	2,263
Noninvestment-grade	1,095	790
Total lending-related commitments	4,167	3,053
Allowance for lending-related commitments	8	14
Guarantee liability	0	0
Total carrying value	8	14
Commitments with collateral	$ 886	$ 498