Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Amortized Cost
AFS securities: Amortized cost, total	$ 93,167	$ 102,515
HTM securities: Net carrying amount, total	80,439
Investment securities: Amortized cost, total	173,606	182,683
Fair Value
AFS securities: Fair value, total	90,354	102,830
HTM securities: Fair value, total	75,776	79,882
Investment securities: Fair value, total	$ 166,130	182,712
Annualized Average Yield
AFS securities: Annualized average yield, total (as a percent)	1.40%
HTM securities: Annualized average yield, total (as a percent)	1.80%
Investment securities: Annualized average yield, total (as a percent)	1.60%
U.S. Treasury securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 8,901
AFS securities: Amortized cost, after 1 year through 5 years	45,839
AFS securities: Amortized cost, after 5 years through 10 years	3,233
AFS securities: Amortized cost, total	57,973	58,974
HTM securities: Net carrying amount, due within 1 year	3,749
HTM securities: Net carrying amount, after 1 year through 5 years	19,336
HTM securities: Net carrying amount, after 5 year through 10 years	4,879
HTM securities: Net carrying amount, after 10 years	1,562
HTM securities: Net carrying amount, total	29,526
Fair Value
AFS securities: Fair value, due within 1 year	8,911
AFS securities: Fair value, after 1 year through 5 years	44,349
AFS securities: Fair value, after 5 years through 10 years	3,219
AFS securities: Fair value, total	56,479	59,021
HTM securities: Fair value, due within 1 year	3,761
HTM securities: Fair value, after 1 year through 5 years	18,974
HTM securities: Fair value, after 5 years through 10 years	4,865
HTM securities: Fair value, after 10 years	1,499
HTM securities: Fair value, total	$ 29,099	29,454
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	1.60%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	1.00%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.10%
HTM securities: Annualized average yield, due within 1 year (as a percent)	1.90%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	1.70%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	2.40%
HTM securities: Annualized average yield, after 10 year (as a percent)	2.30%
U.S. agency securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 12
AFS securities: Amortized cost, after 1 year through 5 years	335
AFS securities: Amortized cost, after 5 years through 10 years	1,179
AFS securities: Amortized cost, after 10 years	22,337
AFS securities: Amortized cost, total	23,863	26,780
HTM securities: Net carrying amount, after 5 year through 10 years	456
HTM securities: Net carrying amount, after 10 years	47,200
HTM securities: Net carrying amount, total	47,656
Fair Value
AFS securities: Fair value, due within 1 year	12
AFS securities: Fair value, after 1 year through 5 years	322
AFS securities: Fair value, after 5 years through 10 years	1,148
AFS securities: Fair value, after 10 years	21,251
AFS securities: Fair value, total	22,733	26,813
HTM securities: Fair value, after 5 years through 10 years	450
HTM securities: Fair value, after 10 years	43,132
HTM securities: Fair value, total	$ 43,582	47,136
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	0.50%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	1.20%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.80%
AFS securities: Annualized average yield, after 10 years (as a percent)	1.80%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	2.00%
HTM securities: Annualized average yield, after 10 year (as a percent)	1.70%
Agency CMBS
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 217
AFS securities: Amortized cost, after 1 year through 5 years	1,318
AFS securities: Amortized cost, after 5 years through 10 years	5,339
AFS securities: Amortized cost, after 10 years	1,722
AFS securities: Amortized cost, total	8,596	14,476
HTM securities: Net carrying amount, due within 1 year	78
HTM securities: Net carrying amount, after 1 year through 5 years	1,371
HTM securities: Net carrying amount, after 5 year through 10 years	567
HTM securities: Net carrying amount, after 10 years	150
HTM securities: Net carrying amount, total	2,166
Fair Value
AFS securities: Fair value, due within 1 year	217
AFS securities: Fair value, after 1 year through 5 years	1,298
AFS securities: Fair value, after 5 years through 10 years	5,337
AFS securities: Fair value, after 10 years	1,597
AFS securities: Fair value, total	8,449	14,676
HTM securities: Fair value, due within 1 year	77
HTM securities: Fair value, after 1 year through 5 years	1,312
HTM securities: Fair value, after 5 years through 10 years	526
HTM securities: Fair value, after 10 years	136
HTM securities: Fair value, total	$ 2,051	2,216
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	1.80%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	1.60%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.80%
AFS securities: Annualized average yield, after 10 years (as a percent)	1.40%
HTM securities: Annualized average yield, due within 1 year (as a percent)	1.10%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	1.30%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.50%
HTM securities: Annualized average yield, after 10 year (as a percent)	1.50%
Non-agency CMBS
Amortized Cost
HTM securities: Net carrying amount, due within 1 year	$ 167
HTM securities: Net carrying amount, after 1 year through 5 years	90
HTM securities: Net carrying amount, after 5 year through 10 years	798
HTM securities: Net carrying amount, after 10 years	36
HTM securities: Net carrying amount, total	1,091
Fair Value
HTM securities: Fair value, due within 1 year	167
HTM securities: Fair value, after 1 year through 5 years	89
HTM securities: Fair value, after 5 years through 10 years	753
HTM securities: Fair value, after 10 years	35
HTM securities: Fair value, total	$ 1,044	1,076
Annualized Average Yield
HTM securities: Annualized average yield, due within 1 year (as a percent)	4.20%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	3.40%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	3.60%
HTM securities: Annualized average yield, after 10 year (as a percent)	4.40%
State and municipal securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 7
AFS securities: Amortized cost, after 1 year through 5 years	24
AFS securities: Amortized cost, after 5 years through 10 years	106
AFS securities: Amortized cost, after 10 years	1,197
AFS securities: Amortized cost, total	1,334	613
Fair Value
AFS securities: Fair value, due within 1 year	7
AFS securities: Fair value, after 1 year through 5 years	25
AFS securities: Fair value, after 5 years through 10 years	103
AFS securities: Fair value, after 10 years	1,167
AFS securities: Fair value, total	$ 1,302	648
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	1.40%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	2.30%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	2.40%
AFS securities: Annualized average yield, after 10 years (as a percent)	2.60%
FFELP student loan ABS:
Amortized Cost
AFS securities: Amortized cost, after 1 year through 5 years	$ 131
AFS securities: Amortized cost, after 5 years through 10 years	139
AFS securities: Amortized cost, after 10 years	1,131
AFS securities: Amortized cost, total	1,401	1,672
Fair Value
AFS securities: Fair value, after 1 year through 5 years	129
AFS securities: Fair value, after 5 years through 10 years	135
AFS securities: Fair value, after 10 years	1,127
AFS securities: Fair value, total	$ 1,391	$ 1,672
Annualized Average Yield
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	0.90%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	0.70%
AFS securities: Annualized average yield, after 10 years (as a percent)	1.20%