Loans - Wholesale Loan Portfolio, Real Estate Class of Loans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 974,260	$ 945,537	$ 974,260	$ 945,537	$ 960,506
Net charge-offs/(recoveries)			2,315	4,209
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 532,786	500,841	$ 532,786	500,841	$ 514,947
% of total criticized to total retained loans secured by real estate	2.79%		2.79%		3.62%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.39%		0.39%		0.64%
Net charge-offs/(recoveries)	$ 37	92	$ 100	553
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,084		2,084		$ 3,318
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 118,167		$ 118,167		$ 119,993
% of total criticized to total retained loans secured by real estate	3.64%		3.64%		3.10%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.32%		0.32%		0.40%
Net charge-offs/(recoveries)	$ 9	(3)	$ 10	9
Wholesale | Secured by real estate | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 4,297		$ 4,297		$ 3,717
% of total criticized to total retained loans secured by real estate	3.64%		3.64%		3.10%
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 375		$ 375		$ 483
% of criticized nonaccrual loans to total retained loans secured by real estate	0.32%		0.32%		0.40%
Wholesale | Secured by real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 72,903		$ 72,903		$ 73,078
Wholesale | Secured by real estate | Multifamily | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,710		$ 1,710		$ 1,144
% of total criticized to total retained loans secured by real estate	2.35%		2.35%		1.57%
Wholesale | Secured by real estate | Multifamily | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 84		$ 84		$ 56
% of criticized nonaccrual loans to total retained loans secured by real estate	0.12%		0.12%		0.08%
Wholesale | Secured by real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 45,264		$ 45,264		$ 46,915
Wholesale | Secured by real estate | Other commercial | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 2,587		$ 2,587		$ 2,573
% of total criticized to total retained loans secured by real estate	5.72%		5.72%		5.48%
Wholesale | Secured by real estate | Other commercial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 291		$ 291		$ 427
% of criticized nonaccrual loans to total retained loans secured by real estate	0.64%		0.64%		0.91%
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 133,476		$ 133,476		$ 142,709
% of total criticized to total retained loans secured by real estate	6.52%		6.52%		9.05%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.74%		0.74%		1.35%
Net charge-offs/(recoveries)	$ 23	95	$ 75	531
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	994		994		$ 1,931
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 281,143		$ 281,143		$ 252,245
% of total criticized to total retained loans secured by real estate	0.66%		0.66%		0.79%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.25%		0.25%		0.36%
Net charge-offs/(recoveries)	$ 5	$ 0	$ 15	$ 13
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 715		$ 715		$ 904