Commitments and Contingencies (Other Commitments) (Details) $ in Millions	Jun. 30, 2026 USD ($)
Broker-Dealer [Abstract]
Collateral securities	$ 837.3
Collateral security (Fair value)	1,200.0
Amount pledged with client-owned securities	526.6
Remaining collateral securities that can be re-pledged, loaned, or sold	645.6
Financial Instruments Owned and Pledged as Collateral [Line Items]
Remaining collateral securities that can be re-pledged, loaned, or sold	645.6
Options Clearing Corporation [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Marketable Securities	15.0
National Securities Clearing Corporation [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Marketable Securities	$ 25.0

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The carrying value as of the balance sheet date of securities received as collateral from a counterparty that were re-pledged, sold, delivered or otherwise reused by the entity.

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Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it is permitted by contract or custom to sell or re-pledge to counterparties as collateral.

+ References

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Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it has sold or re-pledged to counterparties as collateral.

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

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Amount of investment in marketable security.

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