v3.26.1
Compensation - Schedule of Activity Associated with Limited Partnership Units (Details) - shares
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Newmark Holdings Units    
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding    
Beginning balance (in shares) 49,840,356 51,796,454
Issued (in shares) 7,266,067 10,735,416
Redeemed/exchanged units (in shares) (4,934,485) (11,541,874)
Number of units, Forfeited units/other (in shares) (799,155) (1,149,640)
Ending balance (in shares) 51,372,783 49,840,356
Exchangeable units (in shares) 12,767,410 12,378,576
Newmark Holdings Units | Limited Partnership Units    
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding    
Beginning balance (in shares) 2,200,000  
Ending balance (in shares) 1,900,000 2,200,000
Exchangeable partnership units (in shares) 1,200,000 1,400,000
Newmark Holdings Units | Limited Partnership Units | Employee    
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding    
Ending balance (in shares) 2,400,000  
BGC Holdings Units | Limited Partnership Units    
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding    
Ending balance (in shares) 0