Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Amortized Cost
AFS securities: Amortized cost, total	$ 95,042	$ 92,149
HTM securities: Amortized cost, total	64,193
Investment securities: amortized cost, total	159,235	158,843
Fair Value
AFS securities: Fair value, total	91,238	88,113
HTM securities: Fair value, total	53,960	57,453
Investment securities: fair value, total	$ 145,198	145,566
Annualized Average Yield
AFS securities: Annualized average yield, total (as a percent)	3.10%
HTM securities: Annualized average yield, total (as a percent)	2.10%
Investment securities: Annualized average yield, total (as a percent)	2.70%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedges, due within 1 year (as a percent)	2.50%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedge (as a percent)	4.10%
U.S. Treasury securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 16,131
AFS securities: Amortized cost, after 1 year through 5 years	39,883
AFS securities: Amortized cost, after 5 years through 10 years	7,425
AFS securities: Amortized cost, total	63,439	58,484
HTM securities: Amortized cost, due within 1 year	4,896
HTM securities: Amortized cost, after 1 year through 5 years	12,147
HTM securities: Amortized cost, after 5 year through 10 years	503
HTM securities: Amortized cost, after 10 years	1,557
HTM securities: Amortized cost, total	19,103
Fair Value
AFS securities: Fair value, due within 1 year	15,928
AFS securities: Fair value, after 1 year through 5 years	39,427
AFS securities: Fair value, after 5 years through 10 years	7,422
AFS securities: Fair value, total	62,777	57,405
HTM securities: Fair value, due within 1 year	4,788
HTM securities: Fair value, after 1 year through 5 years	11,488
HTM securities: Fair value, after 5 years through 10 years	411
HTM securities: Fair value, after 10 years	1,090
HTM securities: Fair value, total	$ 17,777	21,937
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	1.70%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	3.20%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	4.20%
HTM securities: Annualized average yield, due within 1 year (as a percent)	1.60%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	2.10%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.10%
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	$ 10
AFS securities: Amortized cost, after 1 year through 5 years	313
AFS securities: Amortized cost, after 5 years through 10 years	481
AFS securities: Amortized cost, after 10 years	23,632
AFS securities: Amortized cost, total	24,436	25,852
HTM securities: Amortized cost, after 1 year through 5 years	5
HTM securities: Amortized cost, after 5 year through 10 years	259
HTM securities: Amortized cost, after 10 years	42,207
HTM securities: Amortized cost, total	42,471
Fair Value
AFS securities: Fair value, due within 1 year	10
AFS securities: Fair value, after 1 year through 5 years	296
AFS securities: Fair value, after 5 years through 10 years	439
AFS securities: Fair value, after 10 years	20,962
AFS securities: Fair value, total	21,707	23,328
HTM securities: Fair value, after 1 year through 5 years	5
HTM securities: Fair value, after 5 years through 10 years	242
HTM securities: Fair value, after 10 years	33,555
HTM securities: Fair value, total	$ 33,802	33,195
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	(0.40%)
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)	3.70%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	1.80%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	2.10%
HTM securities: Annualized average yield, after 10 year (as a percent)	2.00%
Agency CMBS
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 1
AFS securities: Amortized cost, after 1 year through 5 years	3,534
AFS securities: Amortized cost, after 5 years through 10 years	1,053
AFS securities: Amortized cost, after 10 years	1,136
AFS securities: Amortized cost, total	5,724	5,871
HTM securities: Amortized cost, due within 1 year	144
HTM securities: Amortized cost, after 1 year through 5 years	894
HTM securities: Amortized cost, after 5 year through 10 years	120
HTM securities: Amortized cost, after 10 years	112
HTM securities: Amortized cost, total	1,270
Fair Value
AFS securities: Fair value, due within 1 year	1
AFS securities: Fair value, after 1 year through 5 years	3,405
AFS securities: Fair value, after 5 years through 10 years	991
AFS securities: Fair value, after 10 years	909
AFS securities: Fair value, total	5,306	5,415
HTM securities: Fair value, due within 1 year	140
HTM securities: Fair value, after 1 year through 5 years	826
HTM securities: Fair value, after 5 years through 10 years	101
HTM securities: Fair value, after 10 years	88
HTM securities: Fair value, total	$ 1,155	1,216
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	(2.20%)
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	2.00%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	2.00%
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)	1.60%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	1.40%
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%
State and municipal securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 29
AFS securities: Amortized cost, after 1 year through 5 years	307
AFS securities: Amortized cost, after 5 years through 10 years	90
AFS securities: Amortized cost, after 10 years	321
AFS securities: Amortized cost, total	747	1,132
Fair Value
AFS securities: Fair value, due within 1 year	29
AFS securities: Fair value, after 1 year through 5 years	306
AFS securities: Fair value, after 5 years through 10 years	90
AFS securities: Fair value, after 10 years	335
AFS securities: Fair value, total	$ 760	1,173
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	5.10%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	4.80%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	5.30%
AFS securities: Annualized average yield, after 10 years (as a percent)	4.30%
FFELP student loan ABS:
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 13
AFS securities: Amortized cost, after 1 year through 5 years	126
AFS securities: Amortized cost, after 5 years through 10 years	28
AFS securities: Amortized cost, after 10 years	529
AFS securities: Amortized cost, total	696	810
Fair Value
AFS securities: Fair value, due within 1 year	13
AFS securities: Fair value, after 1 year through 5 years	122
AFS securities: Fair value, after 5 years through 10 years	28
AFS securities: Fair value, after 10 years	525
AFS securities: Fair value, total	$ 688	792
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	6.00%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	6.30%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	6.30%
AFS securities: Annualized average yield, after 10 years (as a percent)	6.40%
Non-agency CMBS
Amortized Cost
HTM securities: Amortized cost, due within 1 year	$ 169
HTM securities: Amortized cost, after 1 year through 5 years	464
HTM securities: Amortized cost, after 5 year through 10 years	592
HTM securities: Amortized cost, after 10 years	124
HTM securities: Amortized cost, total	1,349
Fair Value
HTM securities: Fair value, due within 1 year	151
HTM securities: Fair value, after 1 year through 5 years	440
HTM securities: Fair value, after 5 years through 10 years	515
HTM securities: Fair value, after 10 years	120
HTM securities: Fair value, total	$ 1,226	$ 1,105
Annualized Average Yield
HTM securities: Annualized average yield, due within 1 year (as a percent)	4.10%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	4.90%
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)	7.00%