Loans and Allowance for Credit Losses - Loans by Portfolio Class and Internal Credit Quality Rating (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Loans by origination year
Total loans	$ 381,819		$ 379,832
Total outstanding commitments	798,918		792,471
Modified loans	1,513	$ 1,532
Pass
Loans by origination year
Total loans	371,275		369,052
Total outstanding commitments	785,384		778,155
Total Criticized
Loans by origination year
Total loans	10,544		10,780
Total outstanding commitments	13,534		14,316
Special Mention
Loans by origination year
Total loans	2,191		2,424
Total outstanding commitments	2,950		3,875
Classified
Loans by origination year
Total loans	8,353		8,356
Total outstanding commitments	10,584		10,441
Loans purchased from GNMA mortgage pools
Loans by origination year
Modified loans	607	652
Commercial | Commercial
Loans by origination year
Originated in 2025/2024	16,577		59,115
Originated in 2024/2023	52,201		19,865
Originated in 2023/2022	15,953		20,319
Originated in 2022/2021	18,415		4,829
Originated in 2021	4,480
Originated prior to 2021	6,458
Originated prior to 2021			7,031
Revolving	29,997		28,325
Total loans	144,081		139,484
Modified loans	193	353
Commercial | Commercial | Pass
Loans by origination year
Originated in 2025/2024	16,275		57,578
Originated in 2024/2023	50,854		19,128
Originated in 2023/2022	15,423		19,718
Originated in 2022/2021	17,944		4,677
Originated in 2021	4,410
Originated prior to 2021	6,039
Originated prior to 2021			6,812
Revolving	29,017		27,344
Total loans	139,962		135,257
Commercial | Commercial | Total Criticized
Loans by origination year
Originated in 2025/2024	302		1,537
Originated in 2024/2023	1,347		737
Originated in 2023/2022	530		601
Originated in 2022/2021	471		152
Originated in 2021	70
Originated prior to 2021	419
Originated prior to 2021			219
Revolving	980		981
Total loans	4,119		4,227
Commercial | Commercial | Special Mention
Loans by origination year
Originated in 2025/2024	62		503
Originated in 2024/2023	473		173
Originated in 2023/2022	152		231
Originated in 2022/2021	127		60
Originated in 2021	12
Originated prior to 2021	146
Originated prior to 2021			76
Revolving	320		169
Total loans	1,292		1,212
Commercial | Commercial | Classified
Loans by origination year
Originated in 2025/2024	240		1,034
Originated in 2024/2023	874		564
Originated in 2023/2022	378		370
Originated in 2022/2021	344		92
Originated in 2021	58
Originated prior to 2021	273
Originated prior to 2021			143
Revolving	660		812
Total loans	2,827		3,015
Commercial | Commercial real estate
Loans by origination year
Originated in 2025/2024	3,583		11,685
Originated in 2024/2023	10,327		6,015
Originated in 2023/2022	5,648		10,621
Originated in 2022/2021	9,618		6,811
Originated in 2021	6,249
Originated prior to 2021	10,828
Originated prior to 2021			11,578
Revolving	2,078		2,146
Revolving converted to term	3		3
Total loans	48,334		48,859
Modified loans	245	332
Commercial | Commercial real estate | Pass
Loans by origination year
Originated in 2025/2024	3,190		9,652
Originated in 2024/2023	8,731		5,213
Originated in 2023/2022	4,880		9,047
Originated in 2022/2021	8,241		6,515
Originated in 2021	5,883
Originated prior to 2021	9,947
Originated prior to 2021			10,822
Revolving	2,031		2,078
Revolving converted to term	3		3
Total loans	42,906		43,330
Commercial | Commercial real estate | Total Criticized
Loans by origination year
Originated in 2025/2024	393		2,033
Originated in 2024/2023	1,596		802
Originated in 2023/2022	768		1,574
Originated in 2022/2021	1,377		296
Originated in 2021	366
Originated prior to 2021	881
Originated prior to 2021			756
Revolving	47		68
Revolving converted to term	0		0
Total loans	5,428		5,529
Commercial | Commercial real estate | Special Mention
Loans by origination year
Originated in 2025/2024	6		261
Originated in 2024/2023	212		42
Originated in 2023/2022	26		661
Originated in 2022/2021	304		100
Originated in 2021	150
Originated prior to 2021	201
Originated prior to 2021			148
Revolving	0		0
Revolving converted to term	0		0
Total loans	899		1,212
Commercial | Commercial real estate | Classified
Loans by origination year
Originated in 2025/2024	387		1,772
Originated in 2024/2023	1,384		760
Originated in 2023/2022	742		913
Originated in 2022/2021	1,073		196
Originated in 2021	216
Originated prior to 2021	680
Originated prior to 2021			608
Revolving	47		68
Revolving converted to term	0		0
Total loans	4,529		4,317
Consumer | Residential mortgages
Loans by origination year
Originated in 2025/2024	1,906		10,291
Originated in 2024/2023	9,995		8,775
Originated in 2023/2022	8,674		28,527
Originated in 2022/2021	28,269		34,729
Originated in 2021	34,350
Originated prior to 2021	35,713
Originated prior to 2021			36,491
Total loans	118,907		118,813
Modified loans	288	27
Consumer | Residential mortgages | Pass
Loans by origination year
Originated in 2025/2024	1,906		10,291
Originated in 2024/2023	9,993		8,764
Originated in 2023/2022	8,661		28,484
Originated in 2022/2021	28,220		34,694
Originated in 2021	34,316
Originated prior to 2021	35,437
Originated prior to 2021			36,211
Total loans	118,533		118,444
Consumer | Residential mortgages | Total Criticized
Loans by origination year
Originated in 2025/2024	0		0
Originated in 2024/2023	2		11
Originated in 2023/2022	13		43
Originated in 2022/2021	49		35
Originated in 2021	34
Originated prior to 2021	276
Originated prior to 2021			280
Total loans	374		369
Consumer | Residential mortgages | Special Mention
Loans by origination year
Originated in 2025/2024	0		0
Originated in 2024/2023	0		0
Originated in 2023/2022	0		0
Originated in 2022/2021	0		0
Originated in 2021	0
Originated prior to 2021	0
Originated prior to 2021			0
Total loans	0		0
Consumer | Residential mortgages | Classified
Loans by origination year
Originated in 2025/2024	0		0
Originated in 2024/2023	2		11
Originated in 2023/2022	13		43
Originated in 2022/2021	49		35
Originated in 2021	34
Originated prior to 2021	276
Originated prior to 2021			280
Total loans	374		369
Consumer | Residential mortgages | Loans purchased from GNMA mortgage pools | Pass
Loans by origination year
Loans 90 days or more past due	2,500		2,300
Modified loans	1,400		1,400
Consumer | Credit card
Loans by origination year
Total loans	29,223		30,350
Modified loans	137	126
Consumer | Credit card | Pass
Loans by origination year
Total loans	28,814		29,915
Consumer | Credit card | Total Criticized
Loans by origination year
Total loans	409		435
Consumer | Credit card | Special Mention
Loans by origination year
Total loans	0		0
Consumer | Credit card | Classified
Loans by origination year
Total loans	409		435
Consumer | Other retail
Loans by origination year
Originated in 2025/2024	1,456		7,401
Originated in 2024/2023	6,905		3,975
Originated in 2023/2022	3,695		4,096
Originated in 2022/2021	3,707		6,551
Originated in 2021	5,767
Originated prior to 2021	5,111
Originated prior to 2021			5,564
Revolving	13,856		13,966
Revolving converted to term	777		773
Total loans	41,274		42,326
Modified loans	43	$ 42
Consumer | Other retail | Pass
Loans by origination year
Originated in 2025/2024	1,456		7,398
Originated in 2024/2023	6,899		3,966
Originated in 2023/2022	3,685		4,085
Originated in 2022/2021	3,696		6,537
Originated in 2021	5,755
Originated prior to 2021	5,091
Originated prior to 2021			5,543
Revolving	13,741		13,846
Revolving converted to term	737		731
Total loans	41,060		42,106
Consumer | Other retail | Total Criticized
Loans by origination year
Originated in 2025/2024	0		3
Originated in 2024/2023	6		9
Originated in 2023/2022	10		11
Originated in 2022/2021	11		14
Originated in 2021	12
Originated prior to 2021	20
Originated prior to 2021			21
Revolving	115		120
Revolving converted to term	40		42
Total loans	214		220
Consumer | Other retail | Special Mention
Loans by origination year
Originated in 2025/2024	0		0
Originated in 2024/2023	0		0
Originated in 2023/2022	0		0
Originated in 2022/2021	0		0
Originated in 2021	0
Originated prior to 2021	0
Originated prior to 2021			0
Revolving	0		0
Revolving converted to term	0		0
Total loans	0		0
Consumer | Other retail | Classified
Loans by origination year
Originated in 2025/2024	0		3
Originated in 2024/2023	6		9
Originated in 2023/2022	10		11
Originated in 2022/2021	11		14
Originated in 2021	12
Originated prior to 2021	20
Originated prior to 2021			21
Revolving	115		120
Revolving converted to term	40		42
Total loans	$ 214		$ 220