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Compensation - Summary of Activity of Number of Share Equivalent Limited Partnership Units and Post IPO Grants (Detail) - Newmark Holdings, L.P. [Member] - Share Equivalent Limited Partnership Units [Member] - shares | 6 Months Ended | 12 Months Ended
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Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of Units, Balance outstanding at beginning of period | 44,733,487 | 29,413,143 | 29,413,143
Number of Units, Granted | 10,746,929 |  | 19,141,943
Number of Units, Redeemed/exchanged units | (880,960) |  | (3,793,351)
Number of Units, Forfeited units |  |  | (28,248)
Number of Units, Forfeited units/Other units | 4,846,170 |  |
Number of Units, Balance outstanding at end of period | 59,445,626 | 44,700,000 | 44,733,487

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- Definition Number of exchangeable limited partnership units redeemed or exchanged into the Company's class A common stock during the period. + References No definition available. + Details
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- Definition Share-based compensation arrangement by share-based payment award non option equity instruments forfeitures and other. + References No definition available. + 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 Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Net number of non-option equity instruments granted to participants. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of equity instruments other than options outstanding, including both vested and non-vested instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Details
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