Related Party Transactions - Transactions with Other Related Parties (Details) - $ / shares			1 Months Ended						3 Months Ended						9 Months Ended
	May 19, 2025	May 16, 2025	Sep. 30, 2025	Aug. 31, 2025	Jul. 31, 2025	Sep. 30, 2024	Aug. 31, 2024	Jul. 31, 2024	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)			2,225,000	2,014,000	0	1,046,000	4,807,000	2,040,000	4,239,000	17,224,000	3,184,000	7,893,000	10,688,000	11,250,000	24,647,000	29,831,000
Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)									4,236,069			7,013,116			22,808,205	26,264,523
Stock repurchased, weighted average price (in dollars per share)									$ 9.88			$ 9.05			$ 9.34	$ 8.06
Mr. Howard W. Lutnick \| Related Party \| Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)	16,115,102	16,452,850
Stock repurchased, weighted average price (in dollars per share)		$ 9.2082
Mr. Howard W. Lutnick \| Related Party \| Common Class A, Shares Held Directly By Howard W. Lutnick
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)		5,616,612
Mr. Howard W. Lutnick \| Related Party \| Common Class A, Shares Held in the Personal Asset Trust
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)		10,489,582
Mr. Howard W. Lutnick \| Related Party \| Common Class A, Shares Held by the Family Trust
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)		8,908
Mr. Howard W. Lutnick \| Related Party \| Common Class A, Shares Held in A Retirement Account
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)		337,748