Loans - Wholesale Loan Portfolio, Internal Risk Ratings (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,273,047	$ 1,255,688	$ 1,280,870
Loans by origination year
Total retained loans	1,273,047	1,255,688	1,280,870
Gross charge-offs by origination year
Total gross charge-offs	5,107	3,227
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 674,152	668,145	$ 672,472
% of investment-grade to total retained loans	67.49%		68.23%
% of total criticized to total retained loans	3.78%		3.51%
% of criticized nonaccrual to total retained loans	0.49%		0.35%
Loans by origination year
Total retained loans	$ 674,152	668,145	$ 672,472
Gross charge-offs by origination year
Total gross charge-offs	448	$ 294
Wholesale | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	454,958		458,838
Loans by origination year
Total retained loans	454,958		458,838
Wholesale | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	219,194		213,634
Loans by origination year
Total retained loans	219,194		213,634
Wholesale | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	193,736		190,056
Loans by origination year
Total retained loans	193,736		190,056
Wholesale | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	22,169		21,232
Loans by origination year
Total retained loans	22,169		21,232
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,289		2,346
Loans by origination year
Total retained loans	3,289		2,346
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 163,886		$ 162,338
% of investment-grade to total retained loans	71.28%		74.17%
% of total criticized to total retained loans	6.24%		4.74%
% of criticized nonaccrual to total retained loans	0.53%		0.25%
Loans by origination year
Term loans originated in 2024/2023	$ 6,581		$ 15,164
Term loans originated in 2023/2022	15,428		41,453
Term loans originated in 2022/2021	41,080		33,623
Term loans originated in 2021/2020	33,078		20,660
Term loans originated in 2020/2019	19,803		19,664
Term loans originated prior to 2020/2019	45,004		29,026
Revolving loans within the revolving period	2,901		2,746
Revolving loans converted to term loans	11		2
Total retained loans	163,886		162,338
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	1		20
Gross charge-offs originated in 2023/2022	13		48
Gross charge-offs originated in 2022/2021	27		22
Gross charge-offs originated in 2021/2020	0		0
Gross charge-offs originated in 2020/2019	33		23
Gross charge-offs originated prior to 2020/2019	38		78
Gross charge-offs originated within the revolving period	0		0
Gross charge-offs originated converted to term loans	0		1
Total gross charge-offs	112		192
Wholesale | Secured by real estate | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	116,812		120,405
Loans by origination year
Term loans originated in 2024/2023	4,147		10,687
Term loans originated in 2023/2022	10,400		28,874
Term loans originated in 2022/2021	27,215		25,784
Term loans originated in 2021/2020	24,165		16,820
Term loans originated in 2020/2019	16,066		15,677
Term loans originated prior to 2020/2019	33,375		21,108
Revolving loans within the revolving period	1,444		1,455
Revolving loans converted to term loans	0		0
Total retained loans	116,812		120,405
Wholesale | Secured by real estate | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	47,074		41,933
Loans by origination year
Term loans originated in 2024/2023	2,434		4,477
Term loans originated in 2023/2022	5,028		12,579
Term loans originated in 2022/2021	13,865		7,839
Term loans originated in 2021/2020	8,913		3,840
Term loans originated in 2020/2019	3,737		3,987
Term loans originated prior to 2020/2019	11,629		7,918
Revolving loans within the revolving period	1,457		1,291
Revolving loans converted to term loans	11		2
Total retained loans	47,074		41,933
Wholesale | Secured by real estate | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	36,840		34,241
Loans by origination year
Total retained loans	36,840		34,241
Wholesale | Secured by real estate | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	9,370		7,291
Loans by origination year
Total retained loans	9,370		7,291
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 864		$ 401
% of criticized nonaccrual to total retained loans	0.53%		0.25%
Loans by origination year
Total retained loans	$ 864		$ 401
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 166,698		$ 167,166
% of investment-grade to total retained loans	42.48%		43.44%
% of total criticized to total retained loans	7.80%		8.32%
% of criticized nonaccrual to total retained loans	0.97%		0.73%
Loans by origination year
Term loans originated in 2024/2023	$ 19,042		$ 33,765
Term loans originated in 2023/2022	21,741		27,086
Term loans originated in 2022/2021	21,227		13,575
Term loans originated in 2021/2020	11,035		4,280
Term loans originated in 2020/2019	2,784		2,174
Term loans originated prior to 2020/2019	3,104		2,121
Revolving loans within the revolving period	87,690		84,090
Revolving loans converted to term loans	75		75
Total retained loans	166,698		167,166
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	5		25
Gross charge-offs originated in 2023/2022	4		8
Gross charge-offs originated in 2022/2021	67		110
Gross charge-offs originated in 2021/2020	24		55
Gross charge-offs originated in 2020/2019	1		2
Gross charge-offs originated prior to 2020/2019	3		12
Gross charge-offs originated within the revolving period	88		259
Gross charge-offs originated converted to term loans	2		8
Total gross charge-offs	194		479
Wholesale | Commercial and industrial | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	70,806		72,624
Loans by origination year
Term loans originated in 2024/2023	8,308		14,875
Term loans originated in 2023/2022	7,356		10,642
Term loans originated in 2022/2021	7,868		4,276
Term loans originated in 2021/2020	3,414		2,291
Term loans originated in 2020/2019	1,639		1,030
Term loans originated prior to 2020/2019	1,661		1,115
Revolving loans within the revolving period	40,558		38,394
Revolving loans converted to term loans	2		1
Total retained loans	70,806		72,624
Wholesale | Commercial and industrial | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	95,892		94,542
Loans by origination year
Term loans originated in 2024/2023	10,734		18,890
Term loans originated in 2023/2022	14,385		16,444
Term loans originated in 2022/2021	13,359		9,299
Term loans originated in 2021/2020	7,621		1,989
Term loans originated in 2020/2019	1,145		1,144
Term loans originated prior to 2020/2019	1,443		1,006
Revolving loans within the revolving period	47,132		45,696
Revolving loans converted to term loans	73		74
Total retained loans	95,892		94,542
Wholesale | Commercial and industrial | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	82,888		80,637
Loans by origination year
Total retained loans	82,888		80,637
Wholesale | Commercial and industrial | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11,384		12,684
Loans by origination year
Total retained loans	11,384		12,684
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,620		1,221
Loans by origination year
Total retained loans	1,620		1,221
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 343,568		$ 342,968
% of investment-grade to total retained loans	77.81%		77.50%
% of total criticized to total retained loans	0.65%		0.58%
% of criticized nonaccrual to total retained loans	0.23%		0.21%
Loans by origination year
Term loans originated in 2024/2023	$ 23,913		$ 52,392
Term loans originated in 2023/2022	35,815		26,126
Term loans originated in 2022/2021	22,308		16,202
Term loans originated in 2021/2020	12,807		12,271
Term loans originated in 2020/2019	11,948		4,532
Term loans originated prior to 2020/2019	10,892		8,663
Revolving loans within the revolving period	224,489		220,529
Revolving loans converted to term loans	1,396		2,253
Total retained loans	343,568		342,968
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	0		5
Gross charge-offs originated in 2023/2022	36		298
Gross charge-offs originated in 2022/2021	2		8
Gross charge-offs originated in 2021/2020	26		8
Gross charge-offs originated in 2020/2019	41		0
Gross charge-offs originated prior to 2020/2019	36		8
Gross charge-offs originated within the revolving period	1		13
Gross charge-offs originated converted to term loans	0		0
Total gross charge-offs	142		340
Wholesale | Other | Individuals and individual entities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	107,200		106,900
Loans by origination year
Total retained loans	107,200		106,900
Wholesale | Other | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	94,300		87,500
Loans by origination year
Total retained loans	94,300		87,500
Wholesale | Other | SPEs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	83,500		91,200
Loans by origination year
Total retained loans	83,500		91,200
Wholesale | Other | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	267,340		265,809
Loans by origination year
Term loans originated in 2024/2023	16,122		38,338
Term loans originated in 2023/2022	27,693		18,034
Term loans originated in 2022/2021	16,067		10,033
Term loans originated in 2021/2020	8,229		10,099
Term loans originated in 2020/2019	10,129		3,721
Term loans originated prior to 2020/2019	8,656		6,662
Revolving loans within the revolving period	179,160		176,728
Revolving loans converted to term loans	1,284		2,194
Total retained loans	267,340		265,809
Wholesale | Other | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	76,228		77,159
Loans by origination year
Term loans originated in 2024/2023	7,791		14,054
Term loans originated in 2023/2022	8,122		8,092
Term loans originated in 2022/2021	6,241		6,169
Term loans originated in 2021/2020	4,578		2,172
Term loans originated in 2020/2019	1,819		811
Term loans originated prior to 2020/2019	2,236		2,001
Revolving loans within the revolving period	45,329		43,801
Revolving loans converted to term loans	112		59
Total retained loans	76,228		77,159
Wholesale | Other | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	74,008		75,178
Loans by origination year
Total retained loans	74,008		75,178
Wholesale | Other | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,415		1,257
Loans by origination year
Total retained loans	1,415		1,257
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	805		724
Loans by origination year
Total retained loans	$ 805		$ 724