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, 2018	Dec. 31, 2017	Dec. 31, 2016
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 1,039,258	$ 991,482	$ 975,152
Total carrying value	1,409	1,512
Standby letters of credit and other financial guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	26,420	28,492
Noninvestment-grade	7,078	6,734
Total lending-related commitments	33,498	35,226
Allowance for lending-related commitments	167	192
Guarantee liability	354	444
Total carrying value	521	636
Commitments with collateral	17,400	17,421
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Investment-grade	2,079	2,646
Noninvestment-grade	746	1,066
Total lending-related commitments	2,825	3,712
Allowance for lending-related commitments	3	3
Guarantee liability	0	0
Total carrying value	3	3
Commitments with collateral	$ 583	$ 878