ARCOLA REGULATORY REQUIREMENTS - Additional Information (Details) - Arcola $ in Millions	Sep. 30, 2021 USD ($)
Minimum net capital requirement	$ 0.3
Regulatory net capital	515.3
Regulatory net capital, excess net capital	$ 515.0

Minimum amount of net capital required to be maintained by broker-dealer subsidiary to engage in security transaction, calculated under Aggregate Indebtedness Standard.

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

Name:	srt_MinimumNetCapitalRequiredForBrokerDealerSubsidiary1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant