Loans - Wholesale Loan Portfolio, Real Estate Class of Loans (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 960,506	$ 945,601	$ 969,415
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 514,947	$ 481,678	$ 477,023
% of total criticized to total retained loans secured by real estate	3.62%	1.60%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.64%	0.22%
Wholesale | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 3,318	$ 1,057
Wholesale | Secured by real estate
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 119,993	$ 120,418
% of total criticized to total retained loans secured by real estate	3.10%	1.09%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.40%	0.15%
Wholesale | Secured by real estate | Commercial construction and development
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 6,400	$ 6,300
Wholesale | Secured by real estate | Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	73,078	73,840
Wholesale | Secured by real estate | Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	46,915	46,578
Wholesale | Secured by real estate | Criticized
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 3,717	$ 1,314
% of total criticized to total retained loans secured by real estate	3.10%	1.09%
Wholesale | Secured by real estate | Criticized | Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 1,144	$ 340
% of total criticized to total retained loans secured by real estate	1.57%	0.46%
Wholesale | Secured by real estate | Criticized | Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 2,573	$ 974
% of total criticized to total retained loans secured by real estate	5.48%	2.09%
Wholesale | Secured by real estate | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 483	$ 183
% of criticized nonaccrual loans to total retained loans secured by real estate	0.40%	0.15%
Wholesale | Secured by real estate | Criticized nonaccrual | Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 56	$ 28
% of criticized nonaccrual loans to total retained loans secured by real estate	0.08%	0.04%
Wholesale | Secured by real estate | Criticized nonaccrual | Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Retained loans	$ 427	$ 155
% of criticized nonaccrual loans to total retained loans secured by real estate	0.91%	0.33%