Related Party Transactions - Transactions with Executive Officers and Directors (Details) - USD ($)														1 Months Ended				3 Months Ended							12 Months Ended
	Oct. 08, 2024	Oct. 07, 2024	Aug. 08, 2024	Jan. 02, 2024	Sep. 21, 2023	Jul. 01, 2023	Jun. 30, 2023	Jun. 08, 2023	Jun. 02, 2023	May 18, 2023	Apr. 18, 2023	Aug. 11, 2022	Apr. 01, 2021	Dec. 31, 2024	Nov. 30, 2024	Oct. 31, 2024	Apr. 30, 2023	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Mar. 14, 2022
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)														0	0	6,369,000		7,893,000	10,688,000	11,250,000	5,473,000	8,087,000	9,814,000	846,000	36,200,000	24,220,000
Sean A. Windeatt
Related Party Transaction [Line Items]
Number of non-exchangeable LPU-NEWs (in shares)																												135,514
Number of non-exchangeable PLPU (in shares)																												27,826
Average determination price (in dollars per share)																												$ 4.84
Shares authorized to be repurchased (in shares)												135,514
Exchange share price (in dollars per share)												$ 4.08
Number of shares redeemed (in shares)												27,826
Number of shares redeemed, value												$ 134,678
Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)																									31,573,031	23,250,551	27,086,884
Stock repurchased, weighted average price (in dollars per share)																									$ 8.30	$ 4.94
Shares granted in period (in shares)						600,000,000
Related Party
Related Party Transaction [Line Items]
Shares withheld for tax withholding obligation, price per share (in dollars per share)										$ 4.61
Related Party | Exchangeable Limited Partnership Units
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)							1,500,000
Related Party | Class A Common Stock | Share-Based Payment Arrangement
Related Party Transaction [Line Items]
Shares granted in period (in shares)							1,000,000
Related Party | Mr. Windeatt
Related Party Transaction [Line Items]
Shares redeemed in period	$ 0
Related Party | Mr. Windeatt | Newmark Holdings LPU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)	31,700	327,127
Determination amount	$ 27,130
Related Party | Mr. Windeatt | Newmark Holdings PLPU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)	2,953	30,285
Determination amount		$ 278,258
Shares redeemed in period		$ 251,128
Shares granted in period (in shares)		27,332
Related Party | Mr. Windeatt | Class A Common Stock | Newmark Holdings LPU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)		239,428
Related Party | Mr. Windeatt | Class A Common Stock | Newmark Holdings
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)		271,362
Related Party | Reporting Person | Exchangeable Limited Partnership Units
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)								128,279
Stock repurchased, weighted average price (in dollars per share)								$ 4.79
Shares granted in period (in shares)																	128,279
Related Party | Reporting Person | Non-exchangeable LPUs
Related Party Transaction [Line Items]
Shares granted in period (in shares)													128,279
Related Party | Reporting Person | Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)			13,063	136,891	474,808
Stock repurchased, weighted average price (in dollars per share)			$ 9.11	$ 6.98	$ 5.29
Related Party | Mr. Merkel | NPU-CV, PSU-CV & PSU
Related Party Transaction [Line Items]
Shares redeemed in period										$ 0
Related Party | Mr. Merkel | NPSU-CV
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										148,146
Related Party | Mr. Merkel | PSU-CV
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										33,585
Related Party | Mr. Merkel | PSU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										74,896
Related Party | Mr. Merkel | NPPSU-CV & PPSU-CV
Related Party Transaction [Line Items]
Shares redeemed in period										$ 843,750
Related Party | Mr. Merkel | NPPSU-CV
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										148,146
Determination amount										$ 681,250
Related Party | Mr. Merkel | PPSU-CV
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										33,585
Determination amount										$ 162,500
Related Party | Mr. Merkel | Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)									150,000
Stock repurchased, weighted average price (in dollars per share)									$ 4.21
Grants in period, net (in shares)										196,525
Related Party | Mr. Merkel | Class A Common Stock | Share-Based Payment Arrangement
Related Party Transaction [Line Items]
Shares granted in period (in shares)										256,627
Related Party | Mr. Lutnick
Related Party Transaction [Line Items]
Determination amount										$ 6,650,000
Related Party | Mr. Lutnick | PSU
Related Party Transaction [Line Items]
Shares redeemed in period										0
Related Party | Mr. Lutnick | Non-exchangeable PSUs & PPSUs | Prior To 5/18/2023
Related Party Transaction [Line Items]
Determination amount										$ 474,195
Related Party | Mr. Lutnick | Non-exchangeable PSU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										11,332,727
Related Party | Mr. Lutnick | Non-exchangeable PSU | Prior To 5/18/2023
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										7,879,736
Related Party | Mr. Lutnick | Non-exchangeable PPSU | Prior To 5/18/2023
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										103,763
Related Party | Mr. Lutnick | Incrementally Monetized Non-exchangeable PSUs & PPSUs
Related Party Transaction [Line Items]
Shares redeemed in period										$ 6,650,000
Related Party | Mr. Lutnick | Incrementally Monetized Non-exchangeable PSUs & PPSUs | On 5/18/2023
Related Party Transaction [Line Items]
Determination amount										$ 6,175,805
Related Party | Mr. Lutnick | Incrementally Monetized Non-exchangeable PSU | On 5/18/2023
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										3,452,991
Related Party | Mr. Lutnick | Incrementally Monetized Non-exchangeable PPSU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										1,451,805
Related Party | Mr. Lutnick | Incrementally Monetized Non-exchangeable PPSU | On 5/18/2023
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										1,348,042
Related Party | Mr. Lutnick | Exchangeable PSU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										520,380
Related Party | Mr. Lutnick | Non-exchangeable HDU
Related Party Transaction [Line Items]
Shares redeemed in period (in shares)										1,474,930
Related Party | Mr. Lutnick | Non-exchangeable HDU | Newmark
Related Party Transaction [Line Items]
Shares redeemed in period										$ 9,148,000
Related Party | Mr. Lutnick | Non-exchangeable HDU | BGC Parnters
Related Party Transaction [Line Items]
Shares redeemed in period										$ 2,100,000
Related Party | Mr. Lutnick | Class A Common Stock
Related Party Transaction [Line Items]
Grants in period, net (in shares)										5,710,534
Related Party | Mr. Lutnick | Class A Common Stock | Share-Based Payment Arrangement
Related Party Transaction [Line Items]
Grants in period, net (in shares)										232,610
Related Party | Mr. Lutnick | Class A Common Stock | Share-Based Payment Arrangement | Non-exchangeable PSU
Related Party Transaction [Line Items]
Shares granted in period (in shares)										11,332,727
Related Party | Mr. Lutnick | Class A Common Stock | Share-Based Payment Arrangement | Exchangeable PSU
Related Party Transaction [Line Items]
Shares granted in period (in shares)										520,380
Related Party | Ms. Bell | Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)											21,786
Stock repurchased, weighted average price (in dollars per share)											$ 4.59