Reverse repurchase agreements outstanding.

No definition available.

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Namespace Prefix:	bgcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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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.

+ Details

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- Definition

The carrying value of securities purchased to be resold in reverse repurchase transactions as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(2)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 405
-Section 55
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35710563&loc=d3e44140-110984

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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Collateralized Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	$ 54,659,000	$ 0
Reverse repurchase agreements outstanding	54,659,000
Securities loaned	0	95,327,000
CF & Co [Member]
Securities Financing Transaction [Line Items]
Securities loaned	$ 0	$ 95,300,000
CF & Co [Member] \| Minimum [Member]
Securities Financing Transaction [Line Items]
Stated interest rate		1.30%	1.30%
CF & Co [Member] \| Maximum [Member]
Securities Financing Transaction [Line Items]
Stated interest rate		2.00%	2.00%
CF & Co [Member] \| Securities Financing Transaction, Fair Value
Securities Financing Transaction [Line Items]
Securities loaned		$ 95,400,000