XML 137 R121.htm IDEA: XBRL DOCUMENT
v3.20.4

Compensation - Activity Associated with Limited Partnership Units Awarded to BGC Employees (Detail) - LPUs [Member] - shares shares in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of Units, Redeemed | 17,782 | 17,709 | 21,343
BGC Holdings LPUs [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of Units, Redeemed | 16,618 | 17,209 | 18,227
Newmark Holdings LPUs [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of Units, Redeemed | 1,164 | 500 | 3,116

X
- Definition Share-based compensation arrangement by share based payment award non option equity instrument redeemed. + References No definition available. + Details
Name: | bgcp_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentRedeemed
Namespace Prefix: | bgcp_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=bgcp_LimitedPartnershipUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=bgcp_BGCHoldingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=bgcp_NewmarkHoldingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |