Loans - Wholesale Loan Portfolio, Real Estate Class of Loans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 963,665	$ 965,448	$ 963,665	$ 965,448	$ 960,506
Net charge-offs/(recoveries)			1,791	3,029
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 524,855	516,787	$ 524,855	516,787	$ 514,947
% of total criticized to total retained loans secured by real estate	3.07%		3.07%		3.62%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.51%		0.51%		0.64%
Net charge-offs/(recoveries)	$ 10	299	$ 63	461
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,698		2,698		$ 3,318
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 118,023		$ 118,023		$ 119,993
% of total criticized to total retained loans secured by real estate	3.87%		3.87%		3.10%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.41%		0.41%		0.40%
Net charge-offs/(recoveries)	$ 1	12	$ 1	12
Wholesale | Secured by real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	72,341		72,341		$ 73,078
Wholesale | Secured by real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	45,682		45,682		46,915
Wholesale | Secured by real estate | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 4,566		$ 4,566		$ 3,717
% of total criticized to total retained loans secured by real estate	3.87%		3.87%		3.10%
Wholesale | Secured by real estate | Criticized | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,594		$ 1,594		$ 1,144
% of total criticized to total retained loans secured by real estate	2.20%		2.20%		1.57%
Wholesale | Secured by real estate | Criticized | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 2,972		$ 2,972		$ 2,573
% of total criticized to total retained loans secured by real estate	6.51%		6.51%		5.48%
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 489		$ 489		$ 483
% of criticized nonaccrual loans to total retained loans secured by real estate	0.41%		0.41%		0.40%
Wholesale | Secured by real estate | Criticized nonaccrual | Multifamily
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 | Criticized nonaccrual | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 405		$ 405		$ 427
% of criticized nonaccrual loans to total retained loans secured by real estate	0.89%		0.89%		0.91%
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 134,212		$ 134,212		$ 142,709
% of total criticized to total retained loans secured by real estate	7.22%		7.22%		9.05%
% of criticized nonaccrual loans to total retained loans secured by real estate	1.05%		1.05%		1.35%
Net charge-offs/(recoveries)	$ 2	268	$ 52	436
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,413		1,413		$ 1,931
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 272,620		$ 272,620		$ 252,245
% of total criticized to total retained loans secured by real estate	0.68%		0.68%		0.79%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.29%		0.29%		0.36%
Net charge-offs/(recoveries)	$ 7	$ 19	$ 10	$ 13
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 796		$ 796		$ 904