Stock Transactions and Unit Redemptions - Share Repurchases of Class A Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended						3 Months Ended				6 Months Ended
	May 16, 2025	Feb. 05, 2025	Jun. 30, 2025	May 31, 2025	Apr. 30, 2025	Jun. 30, 2024	May 31, 2024	Apr. 30, 2024	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Class of Stock [Line Items]
Total Number of Shares Repurchased (in shares)			12,000	16,115,000	1,097,000	4,102,000	5,031,000	1,555,000	17,224,000	3,184,000	10,688,000	11,250,000	20,408,000	21,938,000
Weighted-Average Price Paid per Share (in dollars per share)			$ 9.75	$ 9.21	$ 9.22	$ 8.21	$ 8.62	$ 7.68		$ 9.36		$ 7.11	$ 9.23	$ 7.70
Approximate Dollar Value of Shares That Could Be Repurchased Under the Program			$ 178,389			$ 183,492			$ 178,389		$ 183,492		$ 178,389	$ 183,492
Aggregate purchase price of Class A common stock													$ 171,635	$ 148,117
Shares withheld to satisfy tax liabilities (in shares)									1,100,000		1,300,000		1,800,000	2,700,000
Weighted-average price of shares withheld for tax liabilities (in dollars per share)									$ 9.22		$ 7.61		$ 9.16	$ 7.81
Class A Common Stock
Class of Stock [Line Items]
Total Number of Shares Repurchased (in shares)									16,127,307		9,431,127		18,572,136	19,251,407
Approximate Dollar Value of Shares That Could Be Repurchased Under the Program			$ 178,400						$ 178,400				$ 178,400
Stock repurchased during period (in shares)									17,200,000		10,700,000		20,400,000	21,900,000
Aggregate purchase price of Class A common stock									$ 158,600		$ 89,000		$ 188,400	$ 168,900
Stock repurchased, weighted average price (in dollars per share)									$ 9.21		$ 8.32		$ 9.23	$ 7.70
Shares withheld to satisfy tax liabilities (in shares)		700,000
Share-based payment arrangement, decrease for tax withholding obligation									$ 12,500		$ 10,300		$ 20,900	$ 21,200
Class A Common Stock | Mr. Howard W. Lutnick | Nonrelated Party
Class of Stock [Line Items]
Total Number of Shares Repurchased (in shares)	16,100,000
Restricted Shares
Class of Stock [Line Items]
Share-based payment arrangement, decrease for tax withholding obligation									$ 10,100		$ 9,600		$ 16,800	$ 21,000