Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and securities segregated, at cost	$ 1,752,483	$ 1,090,443
Capital:
Limited partners units issued (in units)	270,509,658	270,380,314
Limited partners, units outstanding (in units)	270,509,658	270,380,314