Loans - Wholesale Loan Portfolio - Real Estate Class of Loans (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 928,887	$ 969,415	$ 947,651
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 437,507	$ 439,162	$ 423,837
% of total criticized exposure to total retained loans	1.55%	1.33%
% of criticized nonaccrual loans to total real estate retained loans	0.34%	0.26%
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,470	$ 1,150
Wholesale | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 115,826	$ 115,737
% of total criticized exposure to total retained loans	0.75%	0.65%
% of criticized nonaccrual loans to total real estate retained loans	0.06%	0.12%
Wholesale | Real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 79,169	$ 79,184
% of total criticized exposure to total retained loans	0.67%	0.49%
% of criticized nonaccrual loans to total real estate retained loans	0.04%	0.07%
Wholesale | Real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 36,657	$ 36,553
% of total criticized exposure to total retained loans	0.93%	1.00%
% of criticized nonaccrual loans to total real estate retained loans	0.08%	0.21%
Wholesale | Real estate | Criticized exposure
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 873	$ 754
Wholesale | Real estate | Criticized exposure | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	533	388
Wholesale | Real estate | Criticized exposure | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	340	366
Wholesale | Real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	65	134
Wholesale | Real estate | Criticized nonaccrual | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	34	57
Wholesale | Real estate | Criticized nonaccrual | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 31	$ 77