Loans and Allowance for Credit Losses - Loans by Portfolio Class and Internal Credit Quality Rating (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Loans by origination year
Total loans	$ 376,133		$ 376,133		$ 373,835
Total outstanding commitments	781,559		781,559		778,392
Modified loans	1,631	$ 1,123	2,848	$ 1,879
Pass
Loans by origination year
Total loans	362,950		362,950		361,687
Total outstanding commitments	764,699		764,699		762,869
Total Criticized
Loans by origination year
Total loans	13,183		13,183		12,148
Total outstanding commitments	16,860		16,860		15,523
Special Mention
Loans by origination year
Total loans	3,004		3,004		3,564
Total outstanding commitments	4,690		4,690		5,053
Classified
Loans by origination year
Total loans	10,179		10,179		8,584
Total outstanding commitments	12,170		12,170		10,470
Loans purchased from GNMA mortgage pools
Loans by origination year
Modified loans	705	637	1,286	939
Commercial | Commercial
Loans by origination year
Originated in 2024/2023	27,822		27,822		44,706
Originated in 2023/2022	31,751		31,751		40,982
Originated in 2022/2021	30,695		30,695		9,490
Originated in 2021/2020	6,997		6,997		3,332
Originated in 2020	3,006		3,006
Originated prior to 2020	5,055		5,055
Originated prior to 2020					5,542
Revolving	29,922		29,922		27,829
Total loans	135,248		135,248		131,881
Modified loans	276	149	496	318
Commercial | Commercial | Pass
Loans by origination year
Originated in 2024/2023	27,054		27,054		43,023
Originated in 2023/2022	30,508		30,508		40,076
Originated in 2022/2021	29,451		29,451		9,219
Originated in 2021/2020	6,738		6,738		3,169
Originated in 2020	2,843		2,843
Originated prior to 2020	4,948		4,948
Originated prior to 2020					5,303
Revolving	28,585		28,585		26,213
Total loans	130,127		130,127		127,003
Commercial | Commercial | Total Criticized
Loans by origination year
Originated in 2024/2023	768		768		1,683
Originated in 2023/2022	1,243		1,243		906
Originated in 2022/2021	1,244		1,244		271
Originated in 2021/2020	259		259		163
Originated in 2020	163		163
Originated prior to 2020	107		107
Originated prior to 2020					239
Revolving	1,337		1,337		1,616
Total loans	5,121		5,121		4,878
Commercial | Commercial | Special Mention
Loans by origination year
Originated in 2024/2023	272		272		827
Originated in 2023/2022	349		349		274
Originated in 2022/2021	274		274		117
Originated in 2021/2020	143		143		92
Originated in 2020	61		61
Originated prior to 2020	9		9
Originated prior to 2020					30
Revolving	279		279		362
Total loans	1,387		1,387		1,702
Commercial | Commercial | Classified
Loans by origination year
Originated in 2024/2023	496		496		856
Originated in 2023/2022	894		894		632
Originated in 2022/2021	970		970		154
Originated in 2021/2020	116		116		71
Originated in 2020	102		102
Originated prior to 2020	98		98
Originated prior to 2020					209
Revolving	1,058		1,058		1,254
Total loans	3,734		3,734		3,176
Commercial | Commercial real estate
Loans by origination year
Originated in 2024/2023	5,491		5,491		11,519
Originated in 2023/2022	8,514		8,514		13,354
Originated in 2022/2021	12,554		12,554		10,120
Originated in 2021/2020	8,922		8,922		3,935
Originated in 2020	3,406		3,406
Originated prior to 2020	10,566		10,566
Originated prior to 2020					11,836
Revolving	2,434		2,434		2,689
Revolving converted to term	0		0		2
Total loans	51,887		51,887		53,455
Modified loans	476	101	714	109
Commercial | Commercial real estate | Pass
Loans by origination year
Originated in 2024/2023	4,385		4,385		8,848
Originated in 2023/2022	6,788		6,788		11,831
Originated in 2022/2021	10,515		10,515		9,235
Originated in 2021/2020	7,919		7,919		3,797
Originated in 2020	3,218		3,218
Originated prior to 2020	9,550		9,550
Originated prior to 2020					10,759
Revolving	2,365		2,365		2,613
Revolving converted to term	0		0		2
Total loans	44,740		44,740		47,085
Commercial | Commercial real estate | Total Criticized
Loans by origination year
Originated in 2024/2023	1,106		1,106		2,671
Originated in 2023/2022	1,726		1,726		1,523
Originated in 2022/2021	2,039		2,039		885
Originated in 2021/2020	1,003		1,003		138
Originated in 2020	188		188
Originated prior to 2020	1,016		1,016
Originated prior to 2020					1,077
Revolving	69		69		76
Revolving converted to term	0		0		0
Total loans	7,147		7,147		6,370
Commercial | Commercial real estate | Special Mention
Loans by origination year
Originated in 2024/2023	194		194		465
Originated in 2023/2022	160		160		382
Originated in 2022/2021	736		736		500
Originated in 2021/2020	377		377		51
Originated in 2020	44		44
Originated prior to 2020	93		93
Originated prior to 2020					458
Revolving	11		11		6
Revolving converted to term	0		0		0
Total loans	1,615		1,615		1,862
Commercial | Commercial real estate | Classified
Loans by origination year
Originated in 2024/2023	912		912		2,206
Originated in 2023/2022	1,566		1,566		1,141
Originated in 2022/2021	1,303		1,303		385
Originated in 2021/2020	626		626		87
Originated in 2020	144		144
Originated prior to 2020	923		923
Originated prior to 2020					619
Revolving	58		58		70
Revolving converted to term	0		0		0
Total loans	5,532		5,532		4,508
Consumer | Residential mortgages
Loans by origination year
Originated in 2024/2023	5,068		5,068		9,739
Originated in 2023/2022	9,352		9,352		29,163
Originated in 2022/2021	28,915		28,915		36,381
Originated in 2021/2020	35,566		35,566		14,782
Originated in 2020	14,257		14,257
Originated prior to 2020	23,989		23,989
Originated prior to 2020					25,464
Revolving	0		0		1
Total loans	117,147		117,147		115,530
Modified loans	22	89	49	233
Consumer | Residential mortgages | Pass
Loans by origination year
Originated in 2024/2023	5,067		5,067		9,734
Originated in 2023/2022	9,343		9,343		29,146
Originated in 2022/2021	28,891		28,891		36,365
Originated in 2021/2020	35,541		35,541		14,773
Originated in 2020	14,245		14,245
Originated prior to 2020	23,731		23,731
Originated prior to 2020					25,202
Revolving	0		0		1
Total loans	116,818		116,818		115,221
Consumer | Residential mortgages | Total Criticized
Loans by origination year
Originated in 2024/2023	1		1		5
Originated in 2023/2022	9		9		17
Originated in 2022/2021	24		24		16
Originated in 2021/2020	25		25		9
Originated in 2020	12		12
Originated prior to 2020	258		258
Originated prior to 2020					262
Revolving	0		0		0
Total loans	329		329		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	9		9		17
Originated in 2022/2021	24		24		16
Originated in 2021/2020	25		25		9
Originated in 2020	12		12
Originated prior to 2020	258		258
Originated prior to 2020					262
Revolving	0		0		0
Total loans	329		329		309
Consumer | Residential mortgages | Loans purchased from GNMA mortgage pools | Pass
Loans by origination year
Loans 90 days or more past due	1,700		1,700		2,000
Modified loans			1,500		1,200
Consumer | Credit card
Loans by origination year
Total loans	28,715		28,715		28,560
Modified loans	116	91	228	174
Consumer | Credit card | Pass
Loans by origination year
Total loans	28,341		28,341		28,185
Consumer | Credit card | Total Criticized
Loans by origination year
Total loans	374		374		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	374		374		375
Consumer | Other retail
Loans by origination year
Originated in 2024/2023	4,048		4,048		5,188
Originated in 2023/2022	4,560		4,560		5,619
Originated in 2022/2021	4,841		4,841		10,413
Originated in 2021/2020	8,410		8,410		4,550
Originated in 2020	3,441		3,441
Originated prior to 2020	3,357		3,357
Originated prior to 2020					4,028
Revolving	13,707		13,707		13,824
Revolving converted to term	772		772		787
Total loans	43,136		43,136		44,409
Modified loans	36	$ 56	75	$ 106
Consumer | Other retail | Pass
Loans by origination year
Originated in 2024/2023	4,046		4,046		5,184
Originated in 2023/2022	4,554		4,554		5,607
Originated in 2022/2021	4,830		4,830		10,398
Originated in 2021/2020	8,396		8,396		4,541
Originated in 2020	3,434		3,434
Originated prior to 2020	3,339		3,339
Originated prior to 2020					4,008
Revolving	13,600		13,600		13,720
Revolving converted to term	725		725		735
Total loans	42,924		42,924		44,193
Consumer | Other retail | Total Criticized
Loans by origination year
Originated in 2024/2023	2		2		4
Originated in 2023/2022	6		6		12
Originated in 2022/2021	11		11		15
Originated in 2021/2020	14		14		9
Originated in 2020	7		7
Originated prior to 2020	18		18
Originated prior to 2020					20
Revolving	107		107		104
Revolving converted to term	47		47		52
Total loans	212		212		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	2		2
Originated prior to 2020					0
Revolving	0		0		0
Revolving converted to term	0		0		0
Total loans	2		2		0
Consumer | Other retail | Classified
Loans by origination year
Originated in 2024/2023	2		2		4
Originated in 2023/2022	6		6		12
Originated in 2022/2021	11		11		15
Originated in 2021/2020	14		14		9
Originated in 2020	7		7
Originated prior to 2020	16		16
Originated prior to 2020					20
Revolving	107		107		104
Revolving converted to term	47		47		52
Total loans	$ 210		$ 210		$ 216