Goodwill and Other Intangible Assets, Net - Summary of Changes in Carrying Amount of Goodwill by Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Goodwill And Intangible Assets [Line Items]
Beginning Balance	$ 164,874
Acquisitions	1,296
Measurement period adjustments	(1,776)
Cumulative translation adjustment	(710)
Ending Balance	163,684
Financial Services [Member]
Goodwill And Intangible Assets [Line Items]
Measurement period adjustments	100
Financial Services [Member] \| Operating Segments [Member]
Goodwill And Intangible Assets [Line Items]
Beginning Balance	85,005
Acquisitions	1,296
Measurement period adjustments	(83)
Cumulative translation adjustment	(710)
Ending Balance	85,508
Real Estate Services [Member]
Goodwill And Intangible Assets [Line Items]
Measurement period adjustments	1,700
Real Estate Services [Member] \| Operating Segments [Member]
Goodwill And Intangible Assets [Line Items]
Beginning Balance	79,869
Acquisitions
Measurement period adjustments	(1,693)
Cumulative translation adjustment
Ending Balance	$ 78,176

Name:	bgcp_GoodwillAndIntangibleAssetsLineItems
Namespace Prefix:	bgcp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e961-128460

+ Details

Name:	us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

Name:	us-gaap_GoodwillTranslationAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration