Loans, Lending Commitments and Related Allowance for Credit Losses - Past Due Loans Held for Investment before Allowance (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 204,935	$ 204,554
Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	491	393
Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,171	6,758
Corporate | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	46	47
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,689	8,678
Commercial real estate | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	291	185
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	61,339	60,375
Residential real estate | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	138	160
Securities-based lending and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	89,044	89,245
Securities-based lending and Other | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 16	$ 1