Loans - Wholesale Loan Portfolio - Real Estate Class of Loans (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 947,728	$ 969,415	$ 940,440
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 438,468	$ 439,162	$ 420,632
% of total criticized exposure to total retained loans	1.43%	1.33%
% of criticized nonaccrual loans to total real estate retained loans	0.28%	0.26%
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,238	$ 1,150
Wholesale | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 115,603	$ 115,737
% of total criticized exposure to total retained loans	0.78%	0.65%
% of criticized nonaccrual loans to total real estate retained loans	0.08%	0.12%
Wholesale | Real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 78,643	$ 79,184
% of total criticized exposure to total retained loans	0.70%	0.49%
% of criticized nonaccrual loans to total real estate retained loans	0.05%	0.07%
Wholesale | Real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 36,960	$ 36,553
% of total criticized exposure to total retained loans	0.97%	1.00%
% of criticized nonaccrual loans to total real estate retained loans	0.14%	0.21%
Wholesale | Real estate | Criticized exposure
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 906	$ 754
Wholesale | Real estate | Criticized exposure | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	548	388
Wholesale | Real estate | Criticized exposure | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	358	366
Wholesale | Real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	91	134
Wholesale | Real estate | Criticized nonaccrual | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	38	57
Wholesale | Real estate | Criticized nonaccrual | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 53	$ 77