Regulatory Requirements - Additional Information (Details)	9 Months Ended
Sep. 30, 2018 USD ($)
Regulatory Capital Requirements [Abstract]
Minimum net capital required	$ 5,000
Net capital	35,800,000
Excess net capital	$ 34,100,000
Aggregate indebtedness to net capital ratio (percent)	0.7
Description of minimum net capital requirements	The greater of $5,000 or 1/15 of aggregate indebtedness
Minimum net capital requirements (percent)	6.67%

Minimum Net Capital Requirement for Broker-Dealer Subsidiary, Percent

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- Definition

Description of the regulatory requirements for capital adequacy purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

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- Definition

The amount of net capital in excess of the minimum required net capital.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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- Definition

Minimum amount of net capital required to be maintained by entity's broker-dealer subsidiary to engage in securities transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Net capital is equal to the net worth of the broker dealer, less certain items such as exchange memberships, carrying value of securities not readily marketable, haircuts on marketable securities in proprietary accounts, furniture and equipment and other illiquid assets as defined.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Indebtedness divided by net capital.

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