Related Party Transactions - Earn-out Liability (Details) - USD ($)			3 Months Ended			9 Months Ended		12 Months Ended
	Jul. 01, 2024	Apr. 03, 2024	Sep. 30, 2025	Jun. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Fair value of the business combination earn-out liability			$ 63,162,000			$ 63,162,000		$ 77,957,000	$ 76,677,000
Net (gains) losses						10,198,000		34,465,000
Earn-out liabilities, at fair value			50,745,000			50,745,000		64,639,000
Alvarium, TWMH And TIG
Related Party Transaction [Line Items]
Earn-out liabilities, at fair value			11,400,000			11,400,000		23,800,000
Alvarium, TWMH And TIG | Earn-out liability
Related Party Transaction [Line Items]
Fair value of the business combination earn-out liability			11,401,000			11,401,000		23,848,000	62,380,000
Net (gains) losses			6,300,000		$ 9,700,000	12,447,000	$ 48,100,000	38,532,000
East End Advisors, LLC ("EEA")
Related Party Transaction [Line Items]
Total purchase consideration transferred		$ 93,114,000
Earn-out liabilities, at fair value		$ 23,300,000	24,200,000			24,200,000		29,900,000
Cash payment for earnout				$ 7,400,000
East End Advisors, LLC ("EEA") | Earn-out liability
Related Party Transaction [Line Items]
Fair value of the business combination earn-out liability			24,225,000			24,225,000		29,871,000	0
Net (gains) losses			$ (600,000)		$ (5,600,000)	$ (1,741,000)	$ (6,300,000)	(6,563,000)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Gain (loss) on earnout liabilities		Gain (loss) on earnout liabilities	Gain (loss) on earnout liabilities	Gain (loss) on earnout liabilities
Envoi, LLC (“Envoi”)
Related Party Transaction [Line Items]
Total purchase consideration transferred	$ 34,258,000
Earn-out liabilities, at fair value	$ 9,000,000.0
Envoi, LLC (“Envoi”) | Envoi earn-out consideration liability
Related Party Transaction [Line Items]
Net (gains) losses			$ (500,000)			$ (600,000)
Earn-out liabilities, at fair value			7,300,000			7,300,000		9,600,000
Envoi, LLC (“Envoi”) | Envoi earn-out growth consideration liability
Related Party Transaction [Line Items]
Net (gains) losses			100,000			300,000
Earn-out liabilities, at fair value			1,100,000			1,100,000		1,300,000
Envoi, LLC (“Envoi”) | Envoi earn-out consideration liability
Related Party Transaction [Line Items]
Fair value of the business combination earn-out liability			7,260,000			7,260,000		9,600,000	0
Net (gains) losses						(613,000)		(1,620,000)
Envoi, LLC (“Envoi”) | Envoi earn-out growth consideration liability
Related Party Transaction [Line Items]
Fair value of the business combination earn-out liability			$ 1,070,000			1,070,000		1,320,000	$ 0
Net (gains) losses						$ 250,000		$ (300,000)