Off-balance Sheet Lending-related Financial Instruments, Guarantees, and Other Commitments - Standby Letters of Credit, Other Financial Guarantees and Other Letters of Credit (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 1,106,247	$ 1,039,258	$ 991,482
Total carrying value	1,593	1,409
Standby letters of credit and other financial guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	26,647	26,420
Noninvestment-grade	7,261	7,078
Total lending-related commitments	33,908	33,498
Allowance for lending-related commitments	216	167
Guarantee liability	402	354
Total carrying value	618	521
Commitments with collateral	17,582	17,400
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	2,136	2,079
Noninvestment-grade	821	746
Total lending-related commitments	2,957	2,825
Allowance for lending-related commitments	4	3
Guarantee liability	0	0
Total carrying value	4	3
Commitments with collateral	$ 726	$ 583