Condensed Consolidated Statements of Financial Condition (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Class A Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	352,840,000	341,745,000
Common stock, shares outstanding	302,315,000	291,475,000
Treasury stock, at cost	50,525,000	50,270,000
Class B Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	45,884,000	45,884,000
Common stock, shares outstanding	45,884,380	45,884,380