HTM Debt Securities, Contractual Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 280,808	$ 272,022
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	1,258
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	16,140
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	16,592
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	246,818
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	264,641	272,386
Held-to-maturity, fair value, remaining contractual maturity, due within one year	1,261
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	16,050
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	16,577
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 230,753
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	2.12%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	2.12%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	2.26%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	2.01%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	2.12%
Securities of U.S. Treasury and federal agencies [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 16,196	16,544
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	12,411
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	3,785
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	15,551	16,825
Held-to-maturity, fair value, remaining contractual maturity, due within one year	0
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	12,386
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	0
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 3,165
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	2.18%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	2.37%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	0.00%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	1.57%
Securities of U.S. states and political subdivisions [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 32,969	32,689
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	1,243
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	2,949
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	2,235
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	26,542
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	30,916	33,475
Held-to-maturity, fair value, remaining contractual maturity, due within one year	1,246
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	2,914
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	2,234
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 24,522
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	2.12%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	2.11%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	1.32%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	2.51%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	2.18%
Federal agency mortgage-backed securities [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 198,266	188,909
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	198,266
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	185,013	187,984
Held-to-maturity, fair value, remaining contractual maturity, due within one year	0
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	0
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	0
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 185,013
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	2.16%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	0.00%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	2.16%
Non-agency mortgage-backed securities [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 1,174	1,082
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	15
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	18
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	30
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	1,111
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	1,115	1,095
Held-to-maturity, fair value, remaining contractual maturity, due within one year	15
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	18
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	29
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 1,053
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	2.97%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	3.24%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	2.93%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	3.16%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	2.97%
Collateralized loan obligations [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 30,475	31,067
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	13,361
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	17,114
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	30,396	31,259
Held-to-maturity, fair value, remaining contractual maturity, due within one year	0
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	0
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	13,396
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 17,000
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	1.65%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	1.73%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	1.59%
Other debt securities [Member]
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]
Held-to-maturity, amortized cost, net	$ 1,728	1,731
Held-to-maturity, amortized cost, net, remaining contractual maturity, due within one year	0
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after one year through five years	762
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after five years through ten years	966
Held-to-maturity, amortized cost, net, remaining contractual maturity, due after ten years	0
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity, fair value	1,650	$ 1,748
Held-to-maturity, fair value, remaining contractual maturity, due within one year	0
Held-to-maturity, fair value, remaining contractual maturity, due after one year through five years	732
Held-to-maturity, fair value, remaining contractual maturity, due after five years through ten years	918
Held-to-maturity, fair value, remaining contractual maturity, due after ten years	$ 0
Debt Securities, Held-to-Maturity, Weighted Average Yield, Maturity [Abstract]
Held-to-maturity weighted average yield	4.47%
Held-to-maturity, weighted average yield, remaining contractual maturity, due within one year	0.00%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after one year through five years	4.13%
Held-to-maturity, weighted average yield, remaining contractual maturity, due after five years through ten years	4.74%
Held-to-maturity, weighed average yield, remaining contractual maturity, due after ten years	0.00%