Netting Arrangements - Narratives (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Fair value of non-cash collateral we pledged	$ 3,800,000,000	$ 4,700,000,000
Fair value of non-cash collateral received	87,000,000,000	46,600,000,000
Fair value of non-cash collateral received that can be resold or repledged	33,500,000,000	46,600,000,000
Fair value of securities received as collateral that have been resold or re-pledged	0	0
Derivative assets not subject to enforceable master netting arrangements	1,000,000	179,000,000
Derivative liabilities not subject to enforceable master netting arrangements	20,000,000	49,000,000
Cash and Cash Equivalents
Derivative [Line Items]
Securities purchased under agreements to resell	53,100,000,000	18,400,000,000
Restricted Cash and Cash Equivalent
Derivative [Line Items]
Securities purchased under agreements to resell	$ 6,300,000,000	$ 0

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

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Fair value of the collateral, or portion thereof, that has been re-pledged, delivered, or otherwise used.

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions where counterparty has the right to re-pledge such.

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Amount, after the effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes purchases of participations in pools of securities that are subject to a resale agreement, assets not subject to a master netting arrangement and not elected to be offset.

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The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

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