Compensation - Grant of Conversion Rights to Newmark Employees (Details) - Limited Partnership Units - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award
Notional value	$ 218,520	$ 194,995
Estimated fair value of limited partnership units	$ 208,029	$ 182,800

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