Commission Management Payable	9 Months Ended
	Sep. 30, 2020
Commission Management Payable [Abstract]
Commission Management Payable	Commission Management PayableThe Company receives a gross commission from various brokers, which is then used to fund commission sharing and recapture arrangements, less the portion retained as income to the Company. Accrued commission sharing and commission recapture payable of $117.8 million and $71.6 million, as of September 30, 2020 and December 31, 2019, respectively, are classified as commission management payable in the accompanying condensed consolidated statements of financial condition.