Loans, Lending Commitments and Related Allowance for Credit Losses - Nonaccrual Loans Held for Investment before Allowance (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 505	$ 591
Nonaccrual loans without an ACL	99	90
Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	149	164
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	84	152
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	108	97
Securities-based lending and Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 164	$ 178