Related Party Transactions - Schedule of Related Party Transactions (Details) - USD ($)	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Equity method investments	$ 135,000		$ 20,403,000
Additional paid-in capital	667,708,000		652,857,000
Series A Preferred Stock
Related Party Transaction [Line Items]
Preferred stock	166,924,000	$ 164,914,000	142,858,000	$ 141,330,000	$ 0	$ 0
Series C Preferred Stock
Related Party Transaction [Line Items]
Preferred stock	172,793,000	$ 168,681,000	160,808,000	$ 157,340,000	$ 153,442,000	$ 0
Related party
Related Party Transaction [Line Items]
Equity method investments	0		20,300,000
Related party | Delayed share purchase agreement
Related Party Transaction [Line Items]
Additional paid-in capital	0		40,000
Related party | Warrants, net of issuance costs | Allianz warrant
Related Party Transaction [Line Items]
Additional paid-in capital	6,591,000		6,591,000
Related party | Warrants, net of issuance costs | Constellation warrant
Related Party Transaction [Line Items]
Additional paid-in capital	3,003,000		3,003,000
Related party | Series A Preferred Stock
Related Party Transaction [Line Items]
Preferred stock	166,924,000		142,858,000
Related party | Series C Preferred Stock
Related Party Transaction [Line Items]
Preferred stock	172,793,000		160,808,000
Other assets | Related party
Related Party Transaction [Line Items]
Related Party Receivables	300,000		500,000
Working capital adjustment in connection with the purchase of Kontora	1,393,000		0
Other assets | Equity method investee
Related Party Transaction [Line Items]
Related Party Receivables	50,000		30,000
Fees receivable, net | Related party | Fees receivable
Related Party Transaction [Line Items]
Related Party Receivables	0		84,000
Delayed share purchase agreement | Related party
Related Party Transaction [Line Items]
Related Party Payables	0		0
Accrued compensation and profit sharing | Related party
Related Party Transaction [Line Items]
Related Party Payables	0		0
Preferred stock tranche liability | Related party
Related Party Transaction [Line Items]
Related Party Payables	(1,650,000)		(3,940,000)
Operating lease liabilities | Related party
Related Party Transaction [Line Items]
Related Party Payables	(1,236,000)		(305,000)
Due from Certain TWMH Members, TIG GP Members and TIG MGMT Members | Other assets | Related party
Related Party Transaction [Line Items]
Related Party Receivables	276,000		435,000
Due from TIG related fee arrangements | Fees receivable, net | Related party | Fees receivable
Related Party Transaction [Line Items]
Related Party Receivables	1,808,000		804,000
Due to Certain TWMH Members, TIG GP Members and TIG MGMT Members | Accrued member distribution payable | Related party
Related Party Transaction [Line Items]
Related Party Payables	(3,260,000)		(3,355,000)
Due to Certain TWMH Members, TIG GP Members and TIG MGMT Members | Other liabilities | Related party
Related Party Transaction [Line Items]
Related Party Payables	(3,300,000)		(3,400,000)
Due to Certain Non-Controlling Interest Holders in Connection with the Tax Receivable Agreements | TRA liability | Related party
Related Party Transaction [Line Items]
Related Party Payables	(32,484,000)		(28,765,000)
PW deferred consideration | Other liabilities | Related party
Related Party Transaction [Line Items]
PW deferred consideration	0		(3,339,000)
Certain Employees | Other liabilities | Related party
Related Party Transaction [Line Items]
Related Party Payables	(740,000)		0
Due to Certain TWMH Members, TIG GP Members, TIG MGMT Members and Alvarium Shareholders in connection with the Business Combination Earn-out | Earn-out liabilities, at fair value | Related party
Related Party Transaction [Line Items]
Related Party Payables	(11,401,000)		(23,848,000)
EEA earn-out liability | Earn-out liabilities, at fair value | Related party
Related Party Transaction [Line Items]
Related Party Payables	(24,225,000)		(29,871,000)
Envoi, LLC (“Envoi”) | Earn-out liabilities, at fair value | Related party | Envoi earn-out consideration liability
Related Party Transaction [Line Items]
Related Party Payables	(7,260,000)		(9,600,000)
Envoi, LLC (“Envoi”) | Earn-out liabilities, at fair value | Related party | Envoi earn-out growth consideration liability
Related Party Transaction [Line Items]
Related Party Payables	(1,070,000)		(1,320,000)
Kontora Family Office GmbH ("Kontora") | Earn-out liabilities, at fair value | Related party
Related Party Transaction [Line Items]
Related Party Payables	$ (6,789,000)		$ 0