AFS and HTM Debt Securities, Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	$ 173,118	$ 175,463
Available-for-sale, gross unrealized gains	819	2,635
Available-for-sale, gross unrealized losses	(5,501)	(854)
Available-for-sale, at fair value	168,436	177,244
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	280,808	272,022
Held-to-maturity, gross unrealized gains	265	3,570
Held-to-maturity, gross unrealized losses	(16,432)	(3,206)
Held-to-maturity, at fair value	264,641	272,386
Total AFS and HTM Debt securities:
Amortized cost, net	453,926	447,485
Debt securities, gross unrealized gains	1,084	6,205
Debt securities, gross unrealized losses	(21,933)	(4,060)
Fair value	433,077	449,630
Allowance for credit loss, available-for-sale debt securities	9	8
Allowance for credit loss, held-to-maturity debt securities	84	96
Securities of U.S. Treasury and federal agencies [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	47,946	39,668
Available-for-sale, gross unrealized gains	91	185
Available-for-sale, gross unrealized losses	(1,604)	(192)
Available-for-sale, at fair value	46,433	39,661
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	16,196	16,544
Held-to-maturity, gross unrealized gains	14	599
Held-to-maturity, gross unrealized losses	(659)	(318)
Held-to-maturity, at fair value	15,551	16,825
Non-U.S. government securities [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	116	71
Available-for-sale, gross unrealized gains	0	0
Available-for-sale, gross unrealized losses	0	0
Available-for-sale, at fair value	116	71
Securities of U.S. states and political subdivisions [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	16,484	16,618
Available-for-sale, gross unrealized gains	271	350
Available-for-sale, gross unrealized losses	(269)	(51)
Available-for-sale, at fair value	16,486	16,917
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	32,969	32,689
Held-to-maturity, gross unrealized gains	69	847
Held-to-maturity, gross unrealized losses	(2,122)	(61)
Held-to-maturity, at fair value	30,916	33,475
Securities of U.S. states and political subdivisions [Member] | Nontaxable preferred debt securities [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	5,300	5,200
Available-for-sale, at fair value	5,300	5,200
Federal agency mortgage-backed securities [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	94,726	104,661
Available-for-sale, gross unrealized gains	245	1,807
Available-for-sale, gross unrealized losses	(3,534)	(582)
Available-for-sale, at fair value	91,437	105,886
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	198,266	188,909
Held-to-maturity, gross unrealized gains	115	1,882
Held-to-maturity, gross unrealized losses	(13,368)	(2,807)
Held-to-maturity, at fair value	185,013	187,984
Non-agency mortgage-backed securities [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	4,641	4,515
Available-for-sale, gross unrealized gains	12	32
Available-for-sale, gross unrealized losses	(45)	(15)
Available-for-sale, at fair value	4,608	4,532
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	1,174	1,082
Held-to-maturity, gross unrealized gains	5	31
Held-to-maturity, gross unrealized losses	(64)	(18)
Held-to-maturity, at fair value	1,115	1,095
Collateralized loan obligations [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	5,231	5,713
Available-for-sale, gross unrealized gains	0	2
Available-for-sale, gross unrealized losses	(34)	(7)
Available-for-sale, at fair value	5,197	5,708
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	30,475	31,067
Held-to-maturity, gross unrealized gains	62	194
Held-to-maturity, gross unrealized losses	(141)	(2)
Held-to-maturity, at fair value	30,396	31,259
Other debt securities [Member]
Available-for-sale debt securities:
Available-for-sale, at amortized cost, net	3,974	4,217
Available-for-sale, gross unrealized gains	200	259
Available-for-sale, gross unrealized losses	(15)	(7)
Available-for-sale, at fair value	4,159	4,469
Held-to-maturity debt securities:
Held-to-maturity, amortized cost, net	1,728	1,731
Held-to-maturity, gross unrealized gains	0	17
Held-to-maturity, gross unrealized losses	(78)	0
Held-to-maturity, at fair value	$ 1,650	$ 1,748