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Compensation - Grant of Conversion Rights to Newmark Employees (Details) - Limited Partnership Units - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award    
Notional value $ 209,528 $ 218,520
Estimated fair value of limited partnership units $ 192,539 $ 208,029