Loans - Wholesale Loan Portfolio, Internal Risk Ratings and Gross Charge-offs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,425,236	$ 1,300,990	$ 1,408,905
Loans by origination year
Total retained loans	1,425,236	1,300,990	1,408,905
Gross charge-offs by origination year
Total gross charge-offs	2,911	2,816
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 818,839	704,714	$ 792,367
% of investment-grade to total retained loans	68.61%		68.32%
% of total criticized to total retained loans	3.65%		3.63%
% of criticized nonaccrual to total retained loans	0.55%		0.56%
Loans by origination year
Total retained loans	$ 818,839	704,714	$ 792,367
Gross charge-offs by origination year
Total gross charge-offs	164	$ 213
Wholesale | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	561,767		541,364
Loans by origination year
Total retained loans	561,767		541,364
Wholesale | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	257,072		251,003
Loans by origination year
Total retained loans	257,072		251,003
Wholesale | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	227,206		222,249
Loans by origination year
Total retained loans	227,206		222,249
Wholesale | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	25,342		24,356
Loans by origination year
Total retained loans	25,342		24,356
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	4,524		4,398
Loans by origination year
Total retained loans	4,524		4,398
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 166,189		$ 165,545
% of investment-grade to total retained loans	72.30%		71.81%
% of total criticized to total retained loans	6.33%		6.37%
% of criticized nonaccrual to total retained loans	1.05%		1.01%
Loans by origination year
Term loans originated in 2026/2025	$ 5,702		$ 24,172
Term loans originated in 2025/2024	24,361		12,472
Term loans originated in 2024/2023	12,204		13,579
Term loans originated in 2023/2022	13,044		34,916
Term loans originated in 2022/2021	33,893		28,644
Term loans originated prior to 2022/2021	73,632		48,370
Revolving loans within the revolving period	3,260		3,299
Revolving loans converted to term loans	93		93
Total retained loans	166,189		165,545
Gross charge-offs by origination year
Gross charge-offs originated in 2026/2025	0		0
Gross charge-offs originated in 2025/2024	0		54
Gross charge-offs originated in 2024/2023	0		13
Gross charge-offs originated in 2023/2022	1		92
Gross charge-offs originated in 2022/2021	4		119
Gross charge-offs originated prior to 2022/2021	20		141
Gross charge-offs originated within the revolving period	0		1
Gross charge-offs originated converted to term loans	0		0
Total gross charge-offs	25		420
Wholesale | Secured by real estate | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	120,160		118,875
Loans by origination year
Term loans originated in 2026/2025	4,094		17,242
Term loans originated in 2025/2024	17,416		9,440
Term loans originated in 2024/2023	8,889		9,187
Term loans originated in 2023/2022	8,936		22,472
Term loans originated in 2022/2021	22,119		22,019
Term loans originated prior to 2022/2021	57,624		37,392
Revolving loans within the revolving period	1,082		1,123
Revolving loans converted to term loans	0		0
Total retained loans	120,160		118,875
Wholesale | Secured by real estate | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	46,029		46,670
Loans by origination year
Term loans originated in 2026/2025	1,608		6,930
Term loans originated in 2025/2024	6,945		3,032
Term loans originated in 2024/2023	3,315		4,392
Term loans originated in 2023/2022	4,108		12,444
Term loans originated in 2022/2021	11,774		6,625
Term loans originated prior to 2022/2021	16,008		10,978
Revolving loans within the revolving period	2,178		2,176
Revolving loans converted to term loans	93		93
Total retained loans	46,029		46,670
Wholesale | Secured by real estate | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	35,508		36,120
Loans by origination year
Total retained loans	35,508		36,120
Wholesale | Secured by real estate | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	8,778		8,872
Loans by origination year
Total retained loans	8,778		8,872
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,743		$ 1,678
% of criticized nonaccrual to total retained loans	1.05%		1.01%
Loans by origination year
Total retained loans	$ 1,743		$ 1,678
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 186,001		$ 174,403
% of investment-grade to total retained loans	38.54%		38.38%
% of total criticized to total retained loans	8.47%		8.37%
% of criticized nonaccrual to total retained loans	1.16%		1.12%
Loans by origination year
Term loans originated in 2026/2025	$ 16,840		$ 49,092
Term loans originated in 2025/2024	42,543		18,794
Term loans originated in 2024/2023	16,021		8,967
Term loans originated in 2023/2022	8,333		9,952
Term loans originated in 2022/2021	7,925		3,842
Term loans originated prior to 2022/2021	5,146		2,050
Revolving loans within the revolving period	89,096		81,605
Revolving loans converted to term loans	97		101
Total retained loans	186,001		174,403
Gross charge-offs by origination year
Gross charge-offs originated in 2026/2025	0		43
Gross charge-offs originated in 2025/2024	0		64
Gross charge-offs originated in 2024/2023	1		11
Gross charge-offs originated in 2023/2022	6		151
Gross charge-offs originated in 2022/2021	1		129
Gross charge-offs originated prior to 2022/2021	8		26
Gross charge-offs originated within the revolving period	65		461
Gross charge-offs originated converted to term loans	1		8
Total gross charge-offs	82		893
Wholesale | Commercial and industrial | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	71,687		66,942
Loans by origination year
Term loans originated in 2026/2025	7,977		16,186
Term loans originated in 2025/2024	12,191		5,418
Term loans originated in 2024/2023	4,485		3,040
Term loans originated in 2023/2022	2,909		4,352
Term loans originated in 2022/2021	3,408		1,836
Term loans originated prior to 2022/2021	2,525		1,225
Revolving loans within the revolving period	38,191		34,884
Revolving loans converted to term loans	1		1
Total retained loans	71,687		66,942
Wholesale | Commercial and industrial | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	114,314		107,461
Loans by origination year
Term loans originated in 2026/2025	8,863		32,906
Term loans originated in 2025/2024	30,352		13,376
Term loans originated in 2024/2023	11,536		5,927
Term loans originated in 2023/2022	5,424		5,600
Term loans originated in 2022/2021	4,517		2,006
Term loans originated prior to 2022/2021	2,621		825
Revolving loans within the revolving period	50,905		46,721
Revolving loans converted to term loans	96		100
Total retained loans	114,314		107,461
Wholesale | Commercial and industrial | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	98,554		92,856
Loans by origination year
Total retained loans	98,554		92,856
Wholesale | Commercial and industrial | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	13,603		12,651
Loans by origination year
Total retained loans	13,603		12,651
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2,157		1,954
Loans by origination year
Total retained loans	2,157		1,954
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 466,649		$ 452,419
% of investment-grade to total retained loans	79.27%		78.59%
% of total criticized to total retained loans	0.77%		0.80%
% of criticized nonaccrual to total retained loans	0.13%		0.17%
Loans by origination year
Term loans originated in 2026/2025	$ 22,941		$ 59,235
Term loans originated in 2025/2024	47,432		19,579
Term loans originated in 2024/2023	16,142		12,364
Term loans originated in 2023/2022	11,112		14,917
Term loans originated in 2022/2021	13,900		7,587
Term loans originated prior to 2022/2021	20,369		14,320
Revolving loans within the revolving period	333,435		324,245
Revolving loans converted to term loans	1,318		172
Total retained loans	466,649		452,419
Gross charge-offs by origination year
Gross charge-offs originated in 2026/2025	0		46
Gross charge-offs originated in 2025/2024	0		195
Gross charge-offs originated in 2024/2023	0		32
Gross charge-offs originated in 2023/2022	0		2
Gross charge-offs originated in 2022/2021	0		9
Gross charge-offs originated prior to 2022/2021	18		58
Gross charge-offs originated within the revolving period	39		26
Gross charge-offs originated converted to term loans	0		106
Total gross charge-offs	57		474
Wholesale | Other | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	246,900		245,100
Loans by origination year
Total retained loans	246,900		245,100
Wholesale | Other | Individuals and individual entities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	147,200		141,100
Loans by origination year
Total retained loans	147,200		141,100
Wholesale | Other | SPEs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	7,600		7,400
Loans by origination year
Total retained loans	7,600		7,400
Wholesale | Other | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	369,920		355,547
Loans by origination year
Term loans originated in 2026/2025	17,443		43,073
Term loans originated in 2025/2024	34,444		13,123
Term loans originated in 2024/2023	10,890		7,939
Term loans originated in 2023/2022	7,109		10,838
Term loans originated in 2022/2021	10,185		5,574
Term loans originated prior to 2022/2021	16,270		11,757
Revolving loans within the revolving period	272,312		263,150
Revolving loans converted to term loans	1,267		93
Total retained loans	369,920		355,547
Wholesale | Other | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	96,729		96,872
Loans by origination year
Term loans originated in 2026/2025	5,498		16,162
Term loans originated in 2025/2024	12,988		6,456
Term loans originated in 2024/2023	5,252		4,425
Term loans originated in 2023/2022	4,003		4,079
Term loans originated in 2022/2021	3,715		2,013
Term loans originated prior to 2022/2021	4,099		2,563
Revolving loans within the revolving period	61,123		61,095
Revolving loans converted to term loans	51		79
Total retained loans	96,729		96,872
Wholesale | Other | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	93,144		93,273
Loans by origination year
Total retained loans	93,144		93,273
Wholesale | Other | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2,961		2,833
Loans by origination year
Total retained loans	2,961		2,833
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	624		766
Loans by origination year
Total retained loans	$ 624		$ 766