Regulatory Capital Requirements - Additional Information (Detail) $ in Millions	Sep. 30, 2025 USD ($)
U.S. Subsidiaries
Brokers And Dealers [Line Items]
Aggregate net capital and financial resources in excess of required level	$ 603.4
Aggregate net capital and financial resources, minimum capital requirement	43.3
U.S. Broker-Dealer Subsidiaries
Brokers And Dealers [Line Items]
Aggregate net capital and financial resources in excess of required level	3.8
Aggregate net capital and financial resources, minimum capital requirement	327.8
Securities reserve deposit	$ 48.4

Brokers and dealers.

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Amount of net capital in excess of minimum required net capital, calculated under Alternative Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

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Minimum amount of net capital of broker-dealer and its subsidiary, calculated under Alternative Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

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Securities deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

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