Marketable Securities (Details) - USD ($)							12 Months Ended
	Jul. 02, 2021	Jun. 25, 2021	Nov. 30, 2020	Dec. 02, 2019	Sep. 26, 2018	Jun. 28, 2013	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Nov. 30, 2019
Marketable Securities
Shares settled (in shares)	944,329		741,505	898,685
Investment owned shares settled fair value	$ 166,000,000		$ 93,500,000	$ 93,500,000
Shares owned (in shares)	5,278,011		250,742	93,562
Gross proceeds from sale of marketable securities							$ 437,820,000	$ 551,064,000	$ 34,738,000
Gain (loss) on marketable securities							(7,470,000)	24,468,000	(2,204,000)
Unrealized gain (loss) on marketable securities							(80,657,000)	77,266,000	$ 5,004,000
Marketable securities							$ 788,000	524,569,000
Cantor
Marketable Securities
Securities loaned, fair value								$ 182,000,000
Common Stock
Marketable Securities
Amount recognized in connection with the earn-out including other income (loss) (in shares)									992,247
Common Stock | Nasdaq
Marketable Securities
Marketable securities		$ 1,093,900,000
Shares received from transaction (in shares)							2,497,831	3,030,922	343,562
Gross proceeds from sale of marketable securities							$ 437,800,000	$ 551,100,000	$ 34,700,000
Gain (loss) on marketable securities							(7,500,000)	24,500,000	(2,200,000)
Unrealized gain (loss) on marketable securities							$ (80,100,000)	$ 77,300,000	$ 5,000,000
Number of shares sold in transaction (in shares)								3,030,922	343,562
Common Stock | Nasdaq | Nasdaq
Marketable Securities
Number of shares pledged to be repurchased (in shares)							0	866,791
Amount received from the value of shares pledged								$ 140,000,000
Common Stock | Nasdaq Earn-Out
Marketable Securities
Shares settled (in shares)	944,329	6,222,340
Marketable securities	$ 166,000,000		$ 121,900,000
Marketable securities										$ 98,600,000
Maximum | Common Stock
Marketable Securities
Remaining earn-out receivable under common stock transaction (in shares)						6,945,729
Minimum | Common Stock
Marketable Securities
Gross revenue on earn-out receivable per year under common stock transaction						$ 25,000,000
Nasdaq Omx | Maximum
Marketable Securities
Shares received from transaction (in shares)					992,247
BGC Partners Inc | Common Stock
Marketable Securities
Period for earn-out receivable under common stock transaction						7 years
BGC Partners Inc | Nasdaq Omx
Marketable Securities
Period for earn-out receivable under common stock transaction						15 years
BGC Partners Inc | Nasdaq Omx | Maximum
Marketable Securities
Earn-out shares receivable under common stock transaction (in shares)						14,883,705
BGC Partners Inc | Nasdaq Omx | Minimum
Marketable Securities
Gross revenue on earn-out receivable per year under common stock transaction						$ 25,000,000