Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost
AFS securities: Amortized cost, total	$ 91,260	$ 92,149
HTM securities: Amortized cost, total	65,420
Investment securities: amortized cost, total	156,680	158,843
Fair Value
AFS securities: Fair value, total	87,313	88,113
HTM securities: Fair value, total	55,283	57,453
Investment securities: fair value, total	$ 142,596	145,566
Annualized Average Yield
AFS securities: Annualized average yield, total (as a percent)	2.90%
HTM securities: Annualized average yield, total (as a percent)	2.00%
Investment securities: Annualized average yield, total (as a percent)	2.50%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedges, due within 1 year (as a percent)	2.10%
AFS securities: Annualized average yield including the interest rate swap accrual of related hedge (as a percent)	3.80%
U.S. Treasury securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 16,765
AFS securities: Amortized cost, after 1 year through 5 years	37,649
AFS securities: Amortized cost, after 5 years through 10 years	4,621
AFS securities: Amortized cost, total	59,035	58,484
HTM securities: Amortized cost, due within 1 year	5,252
HTM securities: Amortized cost, after 1 year through 5 years	13,826
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	21,138
Fair Value
AFS securities: Fair value, due within 1 year	16,508
AFS securities: Fair value, after 1 year through 5 years	37,087
AFS securities: Fair value, after 5 years through 10 years	4,629
AFS securities: Fair value, total	58,224	57,405
HTM securities: Fair value, due within 1 year	5,179
HTM securities: Fair value, after 1 year through 5 years	13,063
HTM securities: Fair value, after 5 years through 10 years	412
HTM securities: Fair value, after 10 years	1,114
HTM securities: Fair value, total	$ 19,768	21,937
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)	2.90%
AFS securities: Annualized average yield, after 5 years through 10 years (as a percent)	4.00%
HTM securities: Annualized average yield, due within 1 year (as a percent)	2.10%
HTM securities: Annualized average yield, after 1 years through 5 years (as a percent)	2.00%
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	349
AFS securities: Amortized cost, after 5 years through 10 years	509
AFS securities: Amortized cost, after 10 years	24,364
AFS securities: Amortized cost, total	25,232	25,852
HTM securities: Amortized cost, after 1 year through 5 years	5
HTM securities: Amortized cost, after 5 year through 10 years	277
HTM securities: Amortized cost, after 10 years	41,416
HTM securities: Amortized cost, total	41,698
Fair Value
AFS securities: Fair value, due within 1 year	9
AFS securities: Fair value, after 1 year through 5 years	327
AFS securities: Fair value, after 5 years through 10 years	464
AFS securities: Fair value, after 10 years	21,710
AFS securities: Fair value, total	22,510	23,328
HTM securities: Fair value, after 1 year through 5 years	5
HTM securities: Fair value, after 5 years through 10 years	258
HTM securities: Fair value, after 10 years	32,917
HTM securities: Fair value, total	$ 33,180	33,195
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)	1.60%
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)	1.90%
Agency CMBS
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 1
AFS securities: Amortized cost, after 1 year through 5 years	2,969
AFS securities: Amortized cost, after 5 years through 10 years	1,615
AFS securities: Amortized cost, after 10 years	1,177
AFS securities: Amortized cost, total	5,762	5,871
HTM securities: Amortized cost, due within 1 year	113
HTM securities: Amortized cost, after 1 year through 5 years	942
HTM securities: Amortized cost, after 5 year through 10 years	116
HTM securities: Amortized cost, after 10 years	126
HTM securities: Amortized cost, total	1,297
Fair Value
AFS securities: Fair value, due within 1 year	1
AFS securities: Fair value, after 1 year through 5 years	2,861
AFS securities: Fair value, after 5 years through 10 years	1,531
AFS securities: Fair value, after 10 years	949
AFS securities: Fair value, total	5,342	5,415
HTM securities: Fair value, due within 1 year	110
HTM securities: Fair value, after 1 year through 5 years	867
HTM securities: Fair value, after 5 years through 10 years	97
HTM securities: Fair value, after 10 years	101
HTM securities: Fair value, total	$ 1,175	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)	1.90%
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)	1.30%
HTM securities: Annualized average yield, after 5 years through 10 years (as a percent)	1.40%
HTM securities: Annualized average yield, after 10 year (as a percent)	1.60%
Non-agency CMBS
Amortized Cost
HTM securities: Amortized cost, due within 1 year	$ 194
HTM securities: Amortized cost, after 1 year through 5 years	391
HTM securities: Amortized cost, after 5 year through 10 years	621
HTM securities: Amortized cost, after 10 years	81
HTM securities: Amortized cost, total	1,287
Fair Value
HTM securities: Fair value, due within 1 year	175
HTM securities: Fair value, after 1 year through 5 years	369
HTM securities: Fair value, after 5 years through 10 years	538
HTM securities: Fair value, after 10 years	78
HTM securities: Fair value, total	$ 1,160	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)	4.70%
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)	6.40%
State and municipal securities
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 27
AFS securities: Amortized cost, after 1 year through 5 years	178
AFS securities: Amortized cost, after 5 years through 10 years	3
AFS securities: Amortized cost, after 10 years	268
AFS securities: Amortized cost, total	476	1,132
Fair Value
AFS securities: Fair value, due within 1 year	27
AFS securities: Fair value, after 1 year through 5 years	179
AFS securities: Fair value, after 5 years through 10 years	5
AFS securities: Fair value, after 10 years	281
AFS securities: Fair value, total	$ 492	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)	4.70%
AFS securities: Annualized average yield, after 10 years (as a percent)	4.50%
FFELP student loan ABS:
Amortized Cost
AFS securities: Amortized cost, due within 1 year	$ 15
AFS securities: Amortized cost, after 1 year through 5 years	135
AFS securities: Amortized cost, after 5 years through 10 years	31
AFS securities: Amortized cost, after 10 years	574
AFS securities: Amortized cost, total	755	810
Fair Value
AFS securities: Fair value, due within 1 year	14
AFS securities: Fair value, after 1 year through 5 years	131
AFS securities: Fair value, after 5 years through 10 years	31
AFS securities: Fair value, after 10 years	569
AFS securities: Fair value, total	$ 745	$ 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)	6.10%
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%