Regulatory Capital Requirements - Additional Information (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Brokers And Dealers [Line Items]
Securities reserve deposit	$ 52.6
U.S. Subsidiaries
Brokers And Dealers [Line Items]
Aggregate net capital and financial resources in excess of required level	505.6
Aggregate net capital and financial resources, minimum capital requirement	31.5
U.S. Broker-Dealer Subsidiaries
Brokers And Dealers [Line Items]
Aggregate net capital and financial resources in excess of required level	295.2
Aggregate net capital and financial resources, minimum capital requirement	$ 3.6

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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