Loans, Lending Commitments and Related Allowance for Credit Losses - Past Due Loans Held for Investment before Allowance (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	$ 144,397	$ 138,619
Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	240	363
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	36,843	35,268
Residential real estate | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	240	332
Securities-based lending and Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	69,206	64,232
Securities-based lending and Other loans | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, gross	$ 0	$ 31