Related Party Transactions - Transactions with Other Related Parties (Details) - USD ($)				1 Months Ended						3 Months Ended				6 Months Ended
	Oct. 06, 2025	May 19, 2025	May 16, 2025	Jun. 30, 2026	May 31, 2026	Apr. 30, 2026	Jun. 30, 2025	May 31, 2025	Apr. 30, 2025	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)				1,805,000	8,401,000	0	12,000	16,115,000	1,097,000		246,000		3,184,000	10,452,000	20,408,000
Mr. Howard W. Lutnick
Related Party Transaction [Line Items]
Shares issued, price per share, after tax (in dollars per share)	$ 0.032		$ 9.2082
Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)										10,203,162		16,127,307		10,449,522	18,572,136
Stock repurchased, weighted average price (in dollars per share)										$ 11.01		$ 9.21		$ 10.97	$ 9.23
Mr. Howard W. Lutnick \| Related Party \| Class A Common Stock
Related Party Transaction [Line Items]
Repurchase of class A common stock (in shares)	337,765	16,115,102	16,452,850
Stock repurchased, weighted average price (in dollars per share)			$ 9.2082
Shares issued, price per share, after tax (in dollars per share)			$ 0.04
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
Purchaser Trusts \| Mr. Howard W. Lutnick
Related Party Transaction [Line Items]
Shares held by related party, value of shares sold	$ 200,000
Cantor \| Class B Common Stock \| Mr. Howard W. Lutnick
Related Party Transaction [Line Items]
Shares issued, price per share, after tax (in dollars per share)	$ 0.032
Shares held by related party, number of shares sold (in shares)	8,973,721
Shares held by related party, shares sold, price per share (in dollars per share)	$ 9.2082
Certain other Trusts Controlled by Mr. Brandon G. Lutnick \| Mr. Howard W. Lutnick
Related Party Transaction [Line Items]
Shares held by related party, value of shares sold	$ 13,096,795.7