Compensation - Activity Associated with Limited Partnership Units (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
NEWMARK Group Inc Parent
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	18,419,613	66,626,185
Number of units, Issued (in shares)	15,402,041	10,143,799
Number of units, Redeemed/exchanged units (in shares)	(2,934,984)	(58,099,726)
Number of units, Forfeited units (in shares)	(198,716)	(250,645)
Ending balance (in shares)	30,687,954	18,419,613
Exchangeable units (in shares)	7,861,359	2,468,443
NEWMARK Group Inc Parent | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	4,200,000
Ending balance (in shares)	3,900,000	4,200,000
Exchangeable partnership units (in shares)	1,500,000	1,300,000
NEWMARK Group Inc Parent | Limited Partnership Units | Employee
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	1,600,000
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	8,663,930	54,422,002
Number of units, Issued (in shares)	25,032	159,057
Number of units, Redeemed/exchanged units (in shares)	(3,169,063)	(45,024,619)
Number of units, Forfeited units (in shares)	(60,511)	(892,510)
Ending balance (in shares)	5,459,388	8,663,930
Exchangeable units (in shares)	2,654,749	3,456,479
BGC Holdings, L.P. | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	6,800,000
Ending balance (in shares)	4,800,000	6,800,000
Exchangeable partnership units (in shares)	2,500,000	3,100,000
BGC Holdings, L.P. | Limited Partnership Units | Employee
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	100,000