Loans - Wholesale Loan Portfolio, Loans Secured by Real Estate (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,285,370	$ 1,280,870	$ 1,265,941
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 687,890	$ 672,472	$ 671,952
% of criticized to total retained loans secured by real estate	3.78%	3.51%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.51%	0.35%
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 3,517	$ 2,346
Wholesale | Secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 163,391	$ 162,338
% of criticized to total retained loans secured by real estate	6.73%	4.74%
% of criticized nonaccrual loans to total retained loans secured by real estate	0.60%	0.25%
Wholesale | Secured by real estate | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 10,993	$ 7,692
% of criticized to total retained loans secured by real estate	6.73%	4.74%
Wholesale | Secured by real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 974	$ 401
% of criticized nonaccrual loans to total retained loans secured by real estate	0.60%	0.25%
Wholesale | Secured by real estate | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 101,744	$ 100,725
Wholesale | Secured by real estate | Multifamily | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 4,589	$ 3,596
% of criticized to total retained loans secured by real estate	4.51%	3.57%
Wholesale | Secured by real estate | Multifamily | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 205	$ 76
% of criticized nonaccrual loans to total retained loans secured by real estate	0.20%	0.08%
Wholesale | Secured by real estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 61,647	$ 61,613
Wholesale | Secured by real estate | Other commercial | Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 6,404	$ 4,096
% of criticized to total retained loans secured by real estate	10.39%	6.65%
Wholesale | Secured by real estate | Other commercial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 769	$ 325
% of criticized nonaccrual loans to total retained loans secured by real estate	1.25%	0.53%