Regulatory Requirements (Detail) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($)
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Minimum period required for financial resources to cover operating costs	1 year
Minimum period required for cash or highly liquid securities to cover operating costs	6 months
Net assets held by regulated subsidiaries	$ 652.0
Amount of capital in excess of aggregate regulatory requirements	$ 331.0

Regulatory requirement minimum period of cash or highly liquid securities to cover operating costs.

No definition available.

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- Definition

Regulatory requirement minimum period of financial resources to cover operating costs.

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of total risk-based capital exceeding minimum required for capital adequacy as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826

+ Details

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- Definition

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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