v3.8.0.1

Net Capital Requirements - Minimum Capital Requirement And Excess Capital (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
US
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital		$ 47.5
Minimum capital requirement		33.3
Excess capital		14.2
UK LTD
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	$ 84.5	83.4
Minimum capital requirement	20.0	22.0
Excess capital	64.5	61.4
Australia
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	11.4	16.6
Minimum capital requirement	1.9	1.1
Excess capital	9.5	15.5
Lucid LLP
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	8.9	10.2
Minimum capital requirement	4.5	4.2
Excess capital	$ 4.4	$ 6.0

The amount of total capital as defined in the regulations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The amount by which the company's Total Capital exceeds the minimum required for capital adequacy purposes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

+ Details

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- Definition

Amount of minimum net capital required to be maintained to engage in securities transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Global Brokerage, Inc. 10-Q