Name:	bgcp_PayableForOpenDerivativeContracts
Namespace Prefix:	bgcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Receivable from net pending trades.

No definition available.

Name:	bgcp_ReceivableFromNetPendingTrades
Namespace Prefix:	bgcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amounts due from broker-dealers, clearing organizations, customers or related broker-dealers related to open derivative contracts.

No definition available.

Name:	bgcp_ReceivableFromOpenDerivativeContracts
Namespace Prefix:	bgcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount payable to other broker-dealer and clearing organization, including, but not limited to, security failed-to-receive, deposit received for security loaned, open transaction, and floor-brokerage payable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

Name:	srt_PayablesToBrokerDealersAndClearingOrganizations
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount payable to broker-dealers or clearing organizations for executing or clearing trades or orders.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126941158&loc=d3e41256-110953

Name:	us-gaap_CommissionsPayableToBrokerDealersAndClearingOrganizations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of other payables due to broker-dealers or clearing organizations.

No definition available.

Name:	us-gaap_OtherPayablesToBrokerDealersAndClearingOrganizations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of other receivables due from broker-dealers or clearing organizations.

No definition available.

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

- References

No definition available.

Name:	us-gaap_PayablesToBrokerDealersAndClearingOrganizationsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount receivable from broker-dealers and clearing organizations, including, but not limited to, securities failed-to-deliver, certain deposits for securities borrowed, open transactions, good faith and margin deposits, commissions and floor brokerage receivables.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 45
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=35710130&loc=d3e41645-110958

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

- References

No definition available.

Name:	us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizationsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of right to receive cash and securities on deposit with clearing organizations. Clearing organizations perform post trade processing and trade comparisons among numerous broker-dealers and act as settlement agents between buying and selling broker-dealers.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 310
-URI https://asc.fasb.org/subtopic&trid=2176284

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

Amount receivable as the result of a fail-to-deliver. A fail-to-deliver is a securities sale to another broker-dealer that has not been delivered to buying broker-dealer by the close of business on the settlement date.

No definition available.

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

Amount payable as the result of fail-to-receive. A fail-to-receive is a securities purchase from another broker-dealer not received from the selling broker-dealer by the close of business on the settlement date.

No definition available.