Loans - Wholesale Loan Portfolio, Real Estate Class of Loans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 948,642	$ 1,003,089	$ 960,506
Net charge-offs/(recoveries)	1,057	1,469
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 514,478	555,289	$ 514,947
% of total criticized to total retained loans secured by real estate	3.68%		3.62%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.59%		0.64%
Net charge-offs/(recoveries)	$ 53	162
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,015		$ 3,318
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 118,538		$ 119,993
% of total criticized to total retained loans secured by real estate	3.59%		3.10%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.42%		0.40%
Net charge-offs/(recoveries)	$ 0	0
Wholesale | Secured by real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	72,194		$ 73,078
Wholesale | Secured by real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	46,344		46,915
Wholesale | Secured by real estate | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 4,258		$ 3,717
% of total criticized to total retained loans secured by real estate	3.59%		3.10%
Wholesale | Secured by real estate | Criticized | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,560		$ 1,144
% of total criticized to total retained loans secured by real estate	2.16%		1.57%
Wholesale | Secured by real estate | Criticized | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 2,698		$ 2,573
% of total criticized to total retained loans secured by real estate	5.82%		5.48%
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 502		$ 483
% of criticized nonaccrual loans to total retained loans secured by real estate	0.42%		0.40%
Wholesale | Secured by real estate | Criticized nonaccrual | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 70		$ 56
% of criticized nonaccrual loans to total retained loans secured by real estate	0.10%		0.08%
Wholesale | Secured by real estate | Criticized nonaccrual | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 432		$ 427
% of criticized nonaccrual loans to total retained loans secured by real estate	0.93%		0.91%
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 139,620		$ 142,709
% of total criticized to total retained loans secured by real estate	9.14%		9.05%
% of criticized nonaccrual loans to total retained loans secured by real estate	1.25%		1.35%
Net charge-offs/(recoveries)	$ 50	168
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,752		$ 1,931
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 256,320		$ 252,245
% of total criticized to total retained loans secured by real estate	0.74%		0.79%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.30%		0.36%
Net charge-offs/(recoveries)	$ 3	$ (6)
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 761		$ 904