Fair Value Disclosures - Schedule of Changes In Fair Value of Level 3 Measurements (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			$ 77,957,000	$ 76,677,000	$ 76,677,000
Issuances			5,743,000		36,848,000
Settlements			(10,340,000)		0
Net (gains) losses			(10,198,000)		(34,465,000)
Transfers out of Level 3			0		(1,103,000)
Ending balance	$ 63,162,000		63,162,000		77,957,000
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			147,568,000	164,077,000	164,077,000
Realized and Unrealized Gains (Losses)			$ 2,299,000		$ (16,509,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		Other loss attributed to non-controlling interests in subsidiaries
Purchases
Ending balance	149,867,000		$ 149,867,000		147,568,000
TRA liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			9,378,000	13,233,000	13,233,000
Issuances			0		0
Settlements			0		0
Net (gains) losses			1,389,000		(3,855,000)
Transfers out of Level 3			0		0
Ending balance	10,767,000		10,767,000		9,378,000
Earn-out liability | Alvarium, TWMH And TIG
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			23,848,000	62,380,000	62,380,000
Issuances			0		0
Settlements			0		0
Net (gains) losses	(6,300,000)	$ (9,700,000)	(12,447,000)	(48,100,000)	(38,532,000)
Transfers out of Level 3			0		0
Ending balance	11,401,000		11,401,000		23,848,000
Earn-out liability | AlTi Wealth Management (Switzerland) SA (“AWMS”)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			0	1,064,000	1,064,000
Issuances					0
Settlements					0
Net (gains) losses					39,000
Transfers out of Level 3					(1,103,000)
Ending balance					0
Earn-out liability | East End Advisors, LLC ("EEA")
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			29,871,000	0	0
Issuances			0		23,308,000
Settlements			(7,387,000)		0
Net (gains) losses	600,000	$ 5,600,000	1,741,000	6,300,000	6,563,000
Transfers out of Level 3			0		0
Ending balance	24,225,000		24,225,000		29,871,000
Earn-out liability | Kontora Family Office GmbH ("Kontora")
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			0
Issuances			5,743,000
Settlements			0
Net (gains) losses	561,000		1,046,000
Transfers out of Level 3			0
Ending balance	6,789,000		6,789,000		0
Envoi earn-out consideration liability | Envoi, LLC (“Envoi”)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			9,600,000	0	0
Issuances			0		7,980,000
Settlements			(2,953,000)		0
Net (gains) losses			613,000		1,620,000
Transfers out of Level 3			0		0
Ending balance	7,260,000		7,260,000		9,600,000
Envoi earn-out growth consideration liability | Envoi, LLC (“Envoi”)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			1,320,000	0	0
Issuances			0		1,020,000
Settlements			0		0
Net (gains) losses			(250,000)		300,000
Transfers out of Level 3			0		0
Ending balance	1,070,000		1,070,000		1,320,000
Preferred stock tranche liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			3,940,000	0	0
Issuances			0		4,540,000
Settlements			0		0
Net (gains) losses			(2,290,000)		(600,000)
Transfers out of Level 3			0		0
Ending balance	1,650,000		1,650,000		3,940,000
Investments – External Strategic Managers
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			147,568,000	$ 164,077,000	164,077,000
Realized and Unrealized Gains (Losses)			2,299,000		(16,509,000)
Purchases					0
Ending balance	$ 149,867,000		$ 149,867,000		$ 147,568,000