Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost
AFS securities: Amortized cost, total	$ 100,685	$ 92,149
HTM securities: Amortized cost, total	62,856
Investment securities: amortized cost, total	163,541	158,843
Fair Value
AFS securities: Fair value, total	97,828	88,113
HTM securities: Fair value, total	54,894	57,453
Investment securities	$ 152,722	145,566
Annualized Average Yield
AFS securities: Annualized average yield, total (as a percent)	3.20%
HTM securities: Annualized average yield, total (as a percent)	2.10%
Investment securities: Annualized average yield, total (as a percent)	2.80%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedges, due within 1 year (as a percent)	2.70%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedge (as a percent)	3.90%
U.S. Treasury securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 18,132
AFS securities: Amortized cost, after 1 year through 5 years	44,001
AFS securities: Amortized cost, after 5 years through 10 years	6,236
AFS securities: Amortized cost, total	68,369	58,484
HTM securities: Amortized cost, due within 1 year	4,596
HTM securities: Amortized cost, after 1 year through 5 years	11,514
HTM securities: Amortized cost, after 5 year through 10 years	503
HTM securities: Amortized cost, after 10 years	1,556
HTM securities: Amortized cost, total	18,169
Fair Value
AFS securities: Fair value, due within 1 year	17,928
AFS securities: Fair value, after 1 year through 5 years	43,834
AFS securities: Fair value, after 5 years through 10 years	6,224
AFS securities: Fair value, total	67,986	57,405
HTM securities: Fair value, due within 1 year	4,524
HTM securities: Fair value, after 1 year through 5 years	11,177
HTM securities: Fair value, after 5 years through 10 years	431
HTM securities: Fair value, after 10 years	1,160
HTM securities: Fair value, total	$ 17,292	21,937
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	2.00%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	3.50%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	4.10%
HTM securities: Annualized average yield, due within 1 year (as a percent)	1.40%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	2.20%
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	277
AFS securities: Amortized cost, after 5 years through 10 years	448
AFS securities: Amortized cost, after 10 years	23,492
AFS securities: Amortized cost, total	24,227	25,852
HTM securities: Amortized cost, after 1 year through 5 years	4
HTM securities: Amortized cost, after 5 year through 10 years	243
HTM securities: Amortized cost, after 10 years	41,820
HTM securities: Amortized cost, total	42,067
Fair Value
AFS securities: Fair value, due within 1 year	10
AFS securities: Fair value, after 1 year through 5 years	268
AFS securities: Fair value, after 5 years through 10 years	420
AFS securities: Fair value, after 10 years	21,437
AFS securities: Fair value, total	22,135	23,328
HTM securities: Fair value, after 1 year through 5 years	4
HTM securities: Fair value, after 5 years through 10 years	232
HTM securities: Fair value, after 10 years	34,921
HTM securities: Fair value, total	$ 35,157	33,195
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	0.70%
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)	2.10%
Agency CMBS
Amortized Cost
AFS securities: Amortized cost, after 1 year through 5 years	$ 3,874
AFS securities: Amortized cost, after 5 years through 10 years	832
AFS securities: Amortized cost, after 10 years	1,122
AFS securities: Amortized cost, total	5,828	5,871
HTM securities: Amortized cost, due within 1 year	320
HTM securities: Amortized cost, after 1 year through 5 years	695
HTM securities: Amortized cost, after 5 year through 10 years	125
HTM securities: Amortized cost, after 10 years	105
HTM securities: Amortized cost, total	1,245
Fair Value
AFS securities: Fair value, after 1 year through 5 years	3,740
AFS securities: Fair value, after 5 years through 10 years	797
AFS securities: Fair value, after 10 years	926
AFS securities: Fair value, total	5,463	5,415
HTM securities: Fair value, due within 1 year	314
HTM securities: Fair value, after 1 year through 5 years	655
HTM securities: Fair value, after 5 years through 10 years	109
HTM securities: Fair value, after 10 years	86
HTM securities: Fair value, total	$ 1,164	1,216
Annualized Average Yield
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	1.90%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.70%
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)	1.90%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	1.20%
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: Amortized cost, due within 1 year	$ 130
HTM securities: Amortized cost, after 1 year through 5 years	476
HTM securities: Amortized cost, after 5 year through 10 years	607
HTM securities: Amortized cost, after 10 years	162
HTM securities: Amortized cost, total	1,375
Fair Value
HTM securities: Fair value, due within 1 year	108
HTM securities: Fair value, after 1 year through 5 years	464
HTM securities: Fair value, after 5 years through 10 years	548
HTM securities: Fair value, after 10 years	161
HTM securities: Fair value, total	$ 1,281	1,105
Annualized Average Yield
HTM securities: Annualized average yield, due within 1 year (as a percent)	3.90%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	5.00%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	3.70%
HTM securities: Annualized average yield, after 10 year (as a percent)	5.50%
State and municipal securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 861
AFS securities: Amortized cost, after 1 year through 5 years	305
AFS securities: Amortized cost, after 5 years through 10 years	95
AFS securities: Amortized cost, after 10 years	359
AFS securities: Amortized cost, total	1,620	1,132
Fair Value
AFS securities: Fair value, due within 1 year	861
AFS securities: Fair value, after 1 year through 5 years	304
AFS securities: Fair value, after 5 years through 10 years	94
AFS securities: Fair value, after 10 years	352
AFS securities: Fair value, total	$ 1,611	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)	4.60%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	4.70%
AFS securities: Annualized average yield, after 10 years (as a percent)	4.00%
FFELP student loan ABS:
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 12
AFS securities: Amortized cost, after 1 year through 5 years	116
AFS securities: Amortized cost, after 5 years through 10 years	25
AFS securities: Amortized cost, after 10 years	488
AFS securities: Amortized cost, total	641	810
Fair Value
AFS securities: Fair value, due within 1 year	12
AFS securities: Fair value, after 1 year through 5 years	113
AFS securities: Fair value, after 5 years through 10 years	24
AFS securities: Fair value, after 10 years	484
AFS securities: Fair value, total	$ 633	$ 792
Annualized Average Yield
AFS securities: Annualized average yield, due within 1 year (as a percent)	5.80%
AFS securities: Annualized average yield, after 1 year through 5 years (as a percent)	6.10%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	5.90%
AFS securities: Annualized average yield, after 10 years (as a percent)	6.30%