Loans - Wholesale Loan Portfolio, Internal Risk Ratings and Gross Charge-offs (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,369,785	$ 1,285,370	$ 1,299,590
Loans by origination year
Total retained loans	1,369,785	1,285,370	1,299,590
Gross charge-offs by origination year
Total gross charge-offs	8,941	7,674
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 764,451	687,890	$ 690,396
% of investment-grade to total retained loans	67.93%		68.32%
% of total criticized to total retained loans	3.46%		3.67%
% of criticized nonaccrual to total retained loans	0.62%		0.57%
Loans by origination year
Total retained loans	$ 764,451	687,890	$ 690,396
Gross charge-offs by origination year
Total gross charge-offs	1,262	$ 659
Wholesale | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	519,281		471,670
Loans by origination year
Total retained loans	519,281		471,670
Wholesale | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	245,170		218,726
Loans by origination year
Total retained loans	245,170		218,726
Wholesale | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	218,682		193,356
Loans by origination year
Total retained loans	218,682		193,356
Wholesale | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	21,748		21,428
Loans by origination year
Total retained loans	21,748		21,428
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	4,740		3,942
Loans by origination year
Total retained loans	4,740		3,942
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 164,371		$ 162,432
% of investment-grade to total retained loans	70.95%		70.36%
% of total criticized to total retained loans	6.37%		6.61%
% of criticized nonaccrual to total retained loans	0.93%		0.89%
Loans by origination year
Term loans originated in 2025/2024	$ 15,730		$ 14,240
Term loans originated in 2024/2023	13,324		15,200
Term loans originated in 2023/2022	14,517		40,001
Term loans originated in 2022/2021	37,137		31,363
Term loans originated in 2021/2020	29,693		19,010
Term loans originated prior to 2021/2020	51,076		39,880
Revolving loans within the revolving period	2,801		2,645
Revolving loans converted to term loans	93		93
Total retained loans	164,371		162,432
Gross charge-offs by origination year
Gross charge-offs originated in 2025/2024	0		72
Gross charge-offs originated in 2024/2023	0		18
Gross charge-offs originated in 2023/2022	1		43
Gross charge-offs originated in 2022/2021	75		2
Gross charge-offs originated in 2021/2020	78		109
Gross charge-offs originated prior to 2021/2020	114		80
Gross charge-offs originated within the revolving period	1		0
Gross charge-offs originated converted to term loans	0		0
Total gross charge-offs	269		324
Wholesale | Secured by real estate | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	116,618		114,280
Loans by origination year
Term loans originated in 2025/2024	11,452		10,002
Term loans originated in 2024/2023	9,784		9,834
Term loans originated in 2023/2022	9,515		25,284
Term loans originated in 2022/2021	23,417		22,796
Term loans originated in 2021/2020	21,854		15,548
Term loans originated prior to 2021/2020	39,494		29,488
Revolving loans within the revolving period	1,102		1,328
Revolving loans converted to term loans	0		0
Total retained loans	116,618		114,280
Wholesale | Secured by real estate | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	47,753		48,152
Loans by origination year
Term loans originated in 2025/2024	4,278		4,238
Term loans originated in 2024/2023	3,540		5,366
Term loans originated in 2023/2022	5,002		14,717
Term loans originated in 2022/2021	13,720		8,567
Term loans originated in 2021/2020	7,839		3,462
Term loans originated prior to 2021/2020	11,582		10,392
Revolving loans within the revolving period	1,699		1,317
Revolving loans converted to term loans	93		93
Total retained loans	47,753		48,152
Wholesale | Secured by real estate | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	37,288		37,422
Loans by origination year
Total retained loans	37,288		37,422
Wholesale | Secured by real estate | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	8,930		9,291
Loans by origination year
Total retained loans	8,930		9,291
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,535		$ 1,439
% of criticized nonaccrual to total retained loans	0.93%		0.89%
Loans by origination year
Total retained loans	$ 1,535		$ 1,439
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 179,585		$ 166,790
% of investment-grade to total retained loans	39.50%		42.49%
% of total criticized to total retained loans	7.40%		7.64%
% of criticized nonaccrual to total retained loans	1.34%		1.06%
Loans by origination year
Term loans originated in 2025/2024	$ 36,283		$ 32,815
Term loans originated in 2024/2023	21,555		17,635
Term loans originated in 2023/2022	10,789		17,530
Term loans originated in 2022/2021	11,973		8,441
Term loans originated in 2021/2020	4,611		1,850
Term loans originated prior to 2021/2020	2,452		2,114
Revolving loans within the revolving period	91,820		86,280
Revolving loans converted to term loans	102		125
Total retained loans	179,585		166,790
Gross charge-offs by origination year
Gross charge-offs originated in 2025/2024	44		25
Gross charge-offs originated in 2024/2023	19		22
Gross charge-offs originated in 2023/2022	7		128
Gross charge-offs originated in 2022/2021	95		24
Gross charge-offs originated in 2021/2020	124		1
Gross charge-offs originated prior to 2021/2020	26		50
Gross charge-offs originated within the revolving period	282		270
Gross charge-offs originated converted to term loans	6		5
Total gross charge-offs	603		525
Wholesale | Commercial and industrial | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	70,936		70,862
Loans by origination year
Term loans originated in 2025/2024	11,835		11,564
Term loans originated in 2024/2023	6,246		6,285
Term loans originated in 2023/2022	3,251		6,588
Term loans originated in 2022/2021	4,944		3,119
Term loans originated in 2021/2020	2,096		1,067
Term loans originated prior to 2021/2020	1,429		1,139
Revolving loans within the revolving period	41,134		41,099
Revolving loans converted to term loans	1		1
Total retained loans	70,936		70,862
Wholesale | Commercial and industrial | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	108,649		95,928
Loans by origination year
Term loans originated in 2025/2024	24,448		21,251
Term loans originated in 2024/2023	15,309		11,350
Term loans originated in 2023/2022	7,538		10,942
Term loans originated in 2022/2021	7,029		5,322
Term loans originated in 2021/2020	2,515		783
Term loans originated prior to 2021/2020	1,023		975
Revolving loans within the revolving period	50,686		45,181
Revolving loans converted to term loans	101		124
Total retained loans	108,649		95,928
Wholesale | Commercial and industrial | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	95,356		83,191
Loans by origination year
Total retained loans	95,356		83,191
Wholesale | Commercial and industrial | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	10,888		10,977
Loans by origination year
Total retained loans	10,888		10,977
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2,405		1,760
Loans by origination year
Total retained loans	2,405		1,760
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 420,495		$ 361,174
% of investment-grade to total retained loans	78.89%		79.33%
% of total criticized to total retained loans	0.65%		0.53%
% of criticized nonaccrual to total retained loans	0.19%		0.21%
Loans by origination year
Term loans originated in 2025/2024	$ 47,094		$ 42,268
Term loans originated in 2024/2023	23,205		24,287
Term loans originated in 2023/2022	14,224		19,190
Term loans originated in 2022/2021	15,464		9,584
Term loans originated in 2021/2020	7,900		9,998
Term loans originated prior to 2021/2020	15,010		9,268
Revolving loans within the revolving period	297,338		244,903
Revolving loans converted to term loans	260		1,676
Total retained loans	420,495		361,174
Gross charge-offs by origination year
Gross charge-offs originated in 2025/2024	31		0
Gross charge-offs originated in 2024/2023	173		38
Gross charge-offs originated in 2023/2022	42		3
Gross charge-offs originated in 2022/2021	2		36
Gross charge-offs originated in 2021/2020	4		40
Gross charge-offs originated prior to 2021/2020	16		50
Gross charge-offs originated within the revolving period	17		6
Gross charge-offs originated converted to term loans	105		0
Total gross charge-offs	390		173
Wholesale | Other | Individuals and individual entities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	131,400		114,800
Loans by origination year
Total retained loans	131,400		114,800
Wholesale | Other | SPEs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	116,400		92,500
Loans by origination year
Total retained loans	116,400		92,500
Wholesale | Other | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	112,700		94,000
Loans by origination year
Total retained loans	112,700		94,000
Wholesale | Other | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	331,727		286,528
Loans by origination year
Term loans originated in 2025/2024	34,425		30,484
Term loans originated in 2024/2023	15,984		17,039
Term loans originated in 2023/2022	9,108		13,272
Term loans originated in 2022/2021	10,927		6,288
Term loans originated in 2021/2020	5,758		8,632
Term loans originated prior to 2021/2020	12,441		7,382
Revolving loans within the revolving period	242,972		201,949
Revolving loans converted to term loans	112		1,482
Total retained loans	331,727		286,528
Wholesale | Other | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	88,768		74,646
Loans by origination year
Term loans originated in 2025/2024	12,669		11,784
Term loans originated in 2024/2023	7,221		7,248
Term loans originated in 2023/2022	5,116		5,918
Term loans originated in 2022/2021	4,537		3,296
Term loans originated in 2021/2020	2,142		1,366
Term loans originated prior to 2021/2020	2,569		1,886
Revolving loans within the revolving period	54,366		42,954
Revolving loans converted to term loans	148		194
Total retained loans	88,768		74,646
Wholesale | Other | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	86,038		72,743
Loans by origination year
Total retained loans	86,038		72,743
Wholesale | Other | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,930		1,160
Loans by origination year
Total retained loans	1,930		1,160
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	800		743
Loans by origination year
Total retained loans	$ 800		$ 743