Loans - Wholesale Loan Portfolio, Internal Risk Ratings (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,285,370	$ 1,265,941	$ 1,280,870
Loans by origination year
Total retained loans	1,285,370	1,265,941	1,280,870
Gross charge-offs by origination year
Total gross charge-offs	7,674	5,096
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 687,890	671,952	$ 672,472
% of investment-grade to total retained loans	67.89%		68.23%
% of total criticized to total retained loans	3.78%		3.51%
% of criticized nonaccrual to total retained loans	0.51%		0.35%
Loans by origination year
Total retained loans	$ 687,890	671,952	$ 672,472
Gross charge-offs by origination year
Total gross charge-offs	659	$ 435
Wholesale | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	467,006		458,838
Loans by origination year
Total retained loans	467,006		458,838
Wholesale | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	220,884		213,634
Loans by origination year
Total retained loans	220,884		213,634
Wholesale | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	194,875		190,056
Loans by origination year
Total retained loans	194,875		190,056
Wholesale | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	22,492		21,232
Loans by origination year
Total retained loans	22,492		21,232
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,517		2,346
Loans by origination year
Total retained loans	3,517		2,346
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 163,391		$ 162,338
% of investment-grade to total retained loans	70.39%		74.17%
% of total criticized to total retained loans	6.73%		4.74%
% of criticized nonaccrual to total retained loans	0.60%		0.25%
Loans by origination year
Term loans originated in 2024/2023	$ 10,041		$ 15,164
Term loans originated in 2023/2022	15,248		41,453
Term loans originated in 2022/2021	40,615		33,623
Term loans originated in 2021/2020	32,296		20,660
Term loans originated in 2020/2019	19,549		19,664
Term loans originated prior to 2020/2019	42,782		29,026
Revolving loans within the revolving period	2,859		2,746
Revolving loans converted to term loans	1		2
Total retained loans	163,391		162,338
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	0		20
Gross charge-offs originated in 2023/2022	18		48
Gross charge-offs originated in 2022/2021	37		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	51		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	139		192
Wholesale | Secured by real estate | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	115,015		120,405
Loans by origination year
Term loans originated in 2024/2023	6,541		10,687
Term loans originated in 2023/2022	10,199		28,874
Term loans originated in 2022/2021	26,053		25,784
Term loans originated in 2021/2020	23,430		16,820
Term loans originated in 2020/2019	15,870		15,677
Term loans originated prior to 2020/2019	31,522		21,108
Revolving loans within the revolving period	1,400		1,455
Revolving loans converted to term loans	0		0
Total retained loans	115,015		120,405
Wholesale | Secured by real estate | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	48,376		41,933
Loans by origination year
Term loans originated in 2024/2023	3,500		4,477
Term loans originated in 2023/2022	5,049		12,579
Term loans originated in 2022/2021	14,562		7,839
Term loans originated in 2021/2020	8,866		3,840
Term loans originated in 2020/2019	3,679		3,987
Term loans originated prior to 2020/2019	11,260		7,918
Revolving loans within the revolving period	1,459		1,291
Revolving loans converted to term loans	1		2
Total retained loans	48,376		41,933
Wholesale | Secured by real estate | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	37,383		34,241
Loans by origination year
Total retained loans	37,383		34,241
Wholesale | Secured by real estate | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	10,019		7,291
Loans by origination year
Total retained loans	10,019		7,291
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 974		$ 401
% of criticized nonaccrual to total retained loans	0.60%		0.25%
Loans by origination year
Total retained loans	$ 974		$ 401
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 164,248		$ 167,166
% of investment-grade to total retained loans	41.39%		43.44%
% of total criticized to total retained loans	7.77%		8.32%
% of criticized nonaccrual to total retained loans	1.06%		0.73%
Loans by origination year
Term loans originated in 2024/2023	$ 24,795		$ 33,765
Term loans originated in 2023/2022	19,495		27,086
Term loans originated in 2022/2021	19,632		13,575
Term loans originated in 2021/2020	9,842		4,280
Term loans originated in 2020/2019	2,257		2,174
Term loans originated prior to 2020/2019	2,720		2,121
Revolving loans within the revolving period	85,439		84,090
Revolving loans converted to term loans	68		75
Total retained loans	164,248		167,166
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	19		25
Gross charge-offs originated in 2023/2022	4		8
Gross charge-offs originated in 2022/2021	116		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	5		12
Gross charge-offs originated within the revolving period	190		259
Gross charge-offs originated converted to term loans	3		8
Total gross charge-offs	362		479
Wholesale | Commercial and industrial | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	67,984		72,624
Loans by origination year
Term loans originated in 2024/2023	9,200		14,875
Term loans originated in 2023/2022	6,762		10,642
Term loans originated in 2022/2021	7,165		4,276
Term loans originated in 2021/2020	3,066		2,291
Term loans originated in 2020/2019	1,362		1,030
Term loans originated prior to 2020/2019	1,480		1,115
Revolving loans within the revolving period	38,948		38,394
Revolving loans converted to term loans	1		1
Total retained loans	67,984		72,624
Wholesale | Commercial and industrial | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	96,264		94,542
Loans by origination year
Term loans originated in 2024/2023	15,595		18,890
Term loans originated in 2023/2022	12,733		16,444
Term loans originated in 2022/2021	12,467		9,299
Term loans originated in 2021/2020	6,776		1,989
Term loans originated in 2020/2019	895		1,144
Term loans originated prior to 2020/2019	1,240		1,006
Revolving loans within the revolving period	46,491		45,696
Revolving loans converted to term loans	67		74
Total retained loans	96,264		94,542
Wholesale | Commercial and industrial | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	83,494		80,637
Loans by origination year
Total retained loans	83,494		80,637
Wholesale | Commercial and industrial | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11,037		12,684
Loans by origination year
Total retained loans	11,037		12,684
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,733		1,221
Loans by origination year
Total retained loans	1,733		1,221
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 360,251		$ 342,968
% of investment-grade to total retained loans	78.84%		77.50%
% of total criticized to total retained loans	0.62%		0.58%
% of criticized nonaccrual to total retained loans	0.22%		0.21%
Loans by origination year
Term loans originated in 2024/2023	$ 35,167		$ 52,392
Term loans originated in 2023/2022	28,637		26,126
Term loans originated in 2022/2021	20,928		16,202
Term loans originated in 2021/2020	11,651		12,271
Term loans originated in 2020/2019	11,067		4,532
Term loans originated prior to 2020/2019	10,140		8,663
Revolving loans within the revolving period	240,858		220,529
Revolving loans converted to term loans	1,803		2,253
Total retained loans	360,251		342,968
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	0		5
Gross charge-offs originated in 2023/2022	38		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	50		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	158		340
Wholesale | Other | Individuals and individual entities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	110,700		106,900
Loans by origination year
Total retained loans	110,700		106,900
Wholesale | Other | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	98,400		87,500
Loans by origination year
Total retained loans	98,400		87,500
Wholesale | Other | SPEs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	91,300		91,200
Loans by origination year
Total retained loans	91,300		91,200
Wholesale | Other | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	284,007		265,809
Loans by origination year
Term loans originated in 2024/2023	25,069		38,338
Term loans originated in 2023/2022	21,517		18,034
Term loans originated in 2022/2021	15,270		10,033
Term loans originated in 2021/2020	7,455		10,099
Term loans originated in 2020/2019	9,325		3,721
Term loans originated prior to 2020/2019	7,838		6,662
Revolving loans within the revolving period	195,968		176,728
Revolving loans converted to term loans	1,565		2,194
Total retained loans	284,007		265,809
Wholesale | Other | Total noninvestment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	76,244		77,159
Loans by origination year
Term loans originated in 2024/2023	10,098		14,054
Term loans originated in 2023/2022	7,120		8,092
Term loans originated in 2022/2021	5,658		6,169
Term loans originated in 2021/2020	4,196		2,172
Term loans originated in 2020/2019	1,742		811
Term loans originated prior to 2020/2019	2,302		2,001
Revolving loans within the revolving period	44,890		43,801
Revolving loans converted to term loans	238		59
Total retained loans	76,244		77,159
Wholesale | Other | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	73,998		75,178
Loans by origination year
Total retained loans	73,998		75,178
Wholesale | Other | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,436		1,257
Loans by origination year
Total retained loans	1,436		1,257
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	810		724
Loans by origination year
Total retained loans	$ 810		$ 724