Loans and Allowance for Credit Losses - Loans by Portfolio Class and Internal Credit Quality Rating (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Loans by origination year
Total loans	$ 374,164		$ 374,164		$ 373,835
Total outstanding commitments	786,855		786,855		778,392
Modified loans	1,540	$ 1,441	3,661	$ 2,946
Pass
Loans by origination year
Total loans	361,434		361,434		361,687
Total outstanding commitments	770,528		770,528		762,869
Total Criticized
Loans by origination year
Total loans	12,730		12,730		12,148
Total outstanding commitments	16,327		16,327		15,523
Special Mention
Loans by origination year
Total loans	2,949		2,949		3,564
Total outstanding commitments	4,499		4,499		5,053
Classified
Loans by origination year
Total loans	9,781		9,781		8,584
Total outstanding commitments	11,828		11,828		10,470
Loans purchased from GNMA mortgage pools
Loans by origination year
Modified loans	588	657	1,640	1,492
Commercial | Commercial
Loans by origination year
Originated in 2024/2023	41,241		41,241		44,706
Originated in 2023/2022	24,306		24,306		40,982
Originated in 2022/2021	24,589		24,589		9,490
Originated in 2021/2020	6,147		6,147		3,332
Originated in 2020	3,102		3,102
Originated prior to 2020	4,516		4,516
Originated prior to 2020					5,542
Revolving	29,737		29,737		27,829
Total loans	133,638		133,638		131,881
Modified loans	318	114	666	249
Commercial | Commercial | Pass
Loans by origination year
Originated in 2024/2023	39,799		39,799		43,023
Originated in 2023/2022	23,359		23,359		40,076
Originated in 2022/2021	23,723		23,723		9,219
Originated in 2021/2020	5,918		5,918		3,169
Originated in 2020	2,962		2,962
Originated prior to 2020	4,417		4,417
Originated prior to 2020					5,303
Revolving	28,497		28,497		26,213
Total loans	128,675		128,675		127,003
Commercial | Commercial | Total Criticized
Loans by origination year
Originated in 2024/2023	1,442		1,442		1,683
Originated in 2023/2022	947		947		906
Originated in 2022/2021	866		866		271
Originated in 2021/2020	229		229		163
Originated in 2020	140		140
Originated prior to 2020	99		99
Originated prior to 2020					239
Revolving	1,240		1,240		1,616
Total loans	4,963		4,963		4,878
Commercial | Commercial | Special Mention
Loans by origination year
Originated in 2024/2023	636		636		827
Originated in 2023/2022	276		276		274
Originated in 2022/2021	169		169		117
Originated in 2021/2020	129		129		92
Originated in 2020	63		63
Originated prior to 2020	13		13
Originated prior to 2020					30
Revolving	263		263		362
Total loans	1,549		1,549		1,702
Commercial | Commercial | Classified
Loans by origination year
Originated in 2024/2023	806		806		856
Originated in 2023/2022	671		671		632
Originated in 2022/2021	697		697		154
Originated in 2021/2020	100		100		71
Originated in 2020	77		77
Originated prior to 2020	86		86
Originated prior to 2020					209
Revolving	977		977		1,254
Total loans	3,414		3,414		3,176
Commercial | Commercial real estate
Loans by origination year
Originated in 2024/2023	8,866		8,866		11,519
Originated in 2023/2022	6,859		6,859		13,354
Originated in 2022/2021	11,991		11,991		10,120
Originated in 2021/2020	7,870		7,870		3,935
Originated in 2020	3,243		3,243
Originated prior to 2020	9,590		9,590
Originated prior to 2020					11,836
Revolving	2,198		2,198		2,689
Revolving converted to term	2		2		2
Total loans	50,619		50,619		53,455
Modified loans	428	435	837	536
Commercial | Commercial real estate | Pass
Loans by origination year
Originated in 2024/2023	7,190		7,190		8,848
Originated in 2023/2022	5,466		5,466		11,831
Originated in 2022/2021	9,964		9,964		9,235
Originated in 2021/2020	7,182		7,182		3,797
Originated in 2020	3,081		3,081
Originated prior to 2020	8,775		8,775
Originated prior to 2020					10,759
Revolving	2,144		2,144		2,613
Revolving converted to term	2		2		2
Total loans	43,804		43,804		47,085
Commercial | Commercial real estate | Total Criticized
Loans by origination year
Originated in 2024/2023	1,676		1,676		2,671
Originated in 2023/2022	1,393		1,393		1,523
Originated in 2022/2021	2,027		2,027		885
Originated in 2021/2020	688		688		138
Originated in 2020	162		162
Originated prior to 2020	815		815
Originated prior to 2020					1,077
Revolving	54		54		76
Revolving converted to term	0		0		0
Total loans	6,815		6,815		6,370
Commercial | Commercial real estate | Special Mention
Loans by origination year
Originated in 2024/2023	260		260		465
Originated in 2023/2022	102		102		382
Originated in 2022/2021	688		688		500
Originated in 2021/2020	183		183		51
Originated in 2020	43		43
Originated prior to 2020	124		124
Originated prior to 2020					458
Revolving	0		0		6
Revolving converted to term	0		0		0
Total loans	1,400		1,400		1,862
Commercial | Commercial real estate | Classified
Loans by origination year
Originated in 2024/2023	1,416		1,416		2,206
Originated in 2023/2022	1,291		1,291		1,141
Originated in 2022/2021	1,339		1,339		385
Originated in 2021/2020	505		505		87
Originated in 2020	119		119
Originated prior to 2020	691		691
Originated prior to 2020					619
Revolving	54		54		70
Revolving converted to term	0		0		0
Total loans	5,415		5,415		4,508
Consumer | Residential mortgages
Loans by origination year
Originated in 2024/2023	7,591		7,591		9,739
Originated in 2023/2022	9,125		9,125		29,163
Originated in 2022/2021	28,786		28,786		36,381
Originated in 2021/2020	35,179		35,179		14,782
Originated in 2020	13,994		13,994
Originated prior to 2020	23,359		23,359
Originated prior to 2020					25,464
Revolving	0		0		1
Total loans	118,034		118,034		115,530
Modified loans	31	65	77	259
Consumer | Residential mortgages | Pass
Loans by origination year
Originated in 2024/2023	7,590		7,590		9,734
Originated in 2023/2022	9,115		9,115		29,146
Originated in 2022/2021	28,756		28,756		36,365
Originated in 2021/2020	35,150		35,150		14,773
Originated in 2020	13,978		13,978
Originated prior to 2020	23,105		23,105
Originated prior to 2020					25,202
Revolving	0		0		1
Total loans	117,694		117,694		115,221
Consumer | Residential mortgages | Total Criticized
Loans by origination year
Originated in 2024/2023	1		1		5
Originated in 2023/2022	10		10		17
Originated in 2022/2021	30		30		16
Originated in 2021/2020	29		29		9
Originated in 2020	16		16
Originated prior to 2020	254		254
Originated prior to 2020					262
Revolving	0		0		0
Total loans	340		340		309
Consumer | Residential mortgages | Special Mention
Loans by origination year
Originated in 2024/2023	0		0		0
Originated in 2023/2022	0		0		0
Originated in 2022/2021	0		0		0
Originated in 2021/2020	0		0		0
Originated in 2020	0		0
Originated prior to 2020	0		0
Originated prior to 2020					0
Revolving	0		0		0
Total loans	0		0		0
Consumer | Residential mortgages | Classified
Loans by origination year
Originated in 2024/2023	1		1		5
Originated in 2023/2022	10		10		17
Originated in 2022/2021	30		30		16
Originated in 2021/2020	29		29		9
Originated in 2020	16		16
Originated prior to 2020	254		254
Originated prior to 2020					262
Revolving	0		0		0
Total loans	340		340		309
Consumer | Residential mortgages | Loans purchased from GNMA mortgage pools | Pass
Loans by origination year
Loans 90 days or more past due	2,000		2,000		2,000
Modified loans			1,400		1,200
Consumer | Credit card
Loans by origination year
Total loans	29,037		29,037		28,560
Modified loans	135	117	332	269
Consumer | Credit card | Pass
Loans by origination year
Total loans	28,641		28,641		28,185
Consumer | Credit card | Total Criticized
Loans by origination year
Total loans	396		396		375
Consumer | Credit card | Special Mention
Loans by origination year
Total loans	0		0		0
Consumer | Credit card | Classified
Loans by origination year
Total loans	396		396		375
Consumer | Other retail
Loans by origination year
Originated in 2024/2023	6,024		6,024		5,188
Originated in 2023/2022	4,259		4,259		5,619
Originated in 2022/2021	4,467		4,467		10,413
Originated in 2021/2020	7,431		7,431		4,550
Originated in 2020	3,036		3,036
Originated prior to 2020	3,075		3,075
Originated prior to 2020					4,028
Revolving	13,775		13,775		13,824
Revolving converted to term	769		769		787
Total loans	42,836		42,836		44,409
Modified loans	40	$ 53	109	$ 141
Consumer | Other retail | Pass
Loans by origination year
Originated in 2024/2023	6,021		6,021		5,184
Originated in 2023/2022	4,251		4,251		5,607
Originated in 2022/2021	4,455		4,455		10,398
Originated in 2021/2020	7,415		7,415		4,541
Originated in 2020	3,031		3,031
Originated prior to 2020	3,059		3,059
Originated prior to 2020					4,008
Revolving	13,663		13,663		13,720
Revolving converted to term	725		725		735
Total loans	42,620		42,620		44,193
Consumer | Other retail | Total Criticized
Loans by origination year
Originated in 2024/2023	3		3		4
Originated in 2023/2022	8		8		12
Originated in 2022/2021	12		12		15
Originated in 2021/2020	16		16		9
Originated in 2020	5		5
Originated prior to 2020	16		16
Originated prior to 2020					20
Revolving	112		112		104
Revolving converted to term	44		44		52
Total loans	216		216		216
Consumer | Other retail | Special Mention
Loans by origination year
Originated in 2024/2023	0		0		0
Originated in 2023/2022	0		0		0
Originated in 2022/2021	0		0		0
Originated in 2021/2020	0		0		0
Originated in 2020	0		0
Originated prior to 2020	0		0
Originated prior to 2020					0
Revolving	0		0		0
Revolving converted to term	0		0		0
Total loans	0		0		0
Consumer | Other retail | Classified
Loans by origination year
Originated in 2024/2023	3		3		4
Originated in 2023/2022	8		8		12
Originated in 2022/2021	12		12		15
Originated in 2021/2020	16		16		9
Originated in 2020	5		5
Originated prior to 2020	16		16
Originated prior to 2020					20
Revolving	112		112		104
Revolving converted to term	44		44		52
Total loans	$ 216		$ 216		$ 216