XML 74 R61.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Limited Partnership Interests in BGC Holdings and Newmark Holdings - Additional Information (Detail) |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 05, 2015 shares | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 shares | Dec. 31, 2018 | Dec. 31, 2017 shares
Noncontrolling Interest [Abstract] |  |  |  |  |  |  |
Number of operating partnerships |  |  |  |  | 2 |  |
Limited partnership interest contribution ratio |  |  |  |  | 45.45% |  |
Payout period for post-termination awards |  |  |  |  | four equal yearly installments |  |
Percentage to preferred units |  |  |  |  | 0.6875% |  |
CF Group Management, Inc. [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Abstract] |  |  |  |  |  |  |
Number of shares, right to exchange from Class A to Class B common stock | 34,649,693 |  |  |  |  |  |
Cantor Rights to Purchase Exchangeable Units [Member] | Maximum [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Abstract] |  |  |  |  |  |  |
Number of shares, right to exchange from Class A to Class B common stock |  |  |  |  | 34,649,693 |  | 34,649,693
Scenario Forecast [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Abstract] |  |  |  |  |  |  |
Percentage to preferred units |  | 0.6875% | 0.6875% | 0.6875% |  | 2.75% |

X
- Definition Class Of Common Stock Exchanged To Another Class Of Common Stock + References No definition available. + Details
Name: | bgcp_ClassOfCommonStockExchangedToAnotherClassOfCommonStock
Namespace Prefix: | bgcp_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Limited partnership interest contribution ratio. + References No definition available. + Details
Name: | bgcp_LimitedPartnershipInterestContributionRatio
Namespace Prefix: | bgcp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of operating partnerships. + References No definition available. + Details
Name: | bgcp_NumberOfOperatingPartnerships
Namespace Prefix: | bgcp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of net profits of consolidated subsidiary allocated to preferred units. + References No definition available. + Details
Name: | bgcp_PercentageOfPreferredPartnershipUnitsAwarded
Namespace Prefix: | bgcp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payout period for post-termination awards. + References No definition available. + Details
Name: | bgcp_PostTerminationAwardPayoutPeriod
Namespace Prefix: | bgcp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_NoncontrollingInterestAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bgcp_CfManagementGroupIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bgcp_CantorRightsToPurchaseExchangeableUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |