Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Provision (reversal) for expected credit losses		$ 4,300,000	$ (2,200,000)	$ 900,000
Guaranty liabilities	$ 30,610,000	30,610,000	26,315,000	28,551,000
Allowance for doubtful accounts, period increase (decrease)		(7,000,000.0)	(5,100,000)	(1,400,000)
Allowance for doubtful accounts	7,400,000	7,400,000	14,400,000
Allowance for credit loss	8,800,000	8,800,000	8,800,000
Other income (loss), net		43,049,000	6,677,000	13,854,000
Gain on insured event		42,300,000
Gain on insured event, gross		50,000,000.0
Legal fees		7,700,000
Revenues		$ 3,294,024,000	2,738,502,000	2,470,368,000
Number of reportable segments | segment		1
Interest income on loans held for sale		$ 48,080,000	37,716,000	28,068,000
Labor and related expense		2,229,518,000	1,783,798,000	1,628,885,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs		282,045,000	185,398,000	139,747,000
Depreciation and amortization		181,303,000	174,299,000	166,221,000
Professional and consulting fees		33,310,000	26,446,000	27,204,000
Interest expense, net		32,482,000	31,768,000	21,737,000
Total assets	$ 5,019,167,000	5,019,167,000	4,710,120,000
Impairment of intangible assets		$ 0	0	0
Payout period for post-termination awards		4 years
Percentage to preferred units	0.6875%	2.75%
Reportable Segment
New Accounting Pronouncements or Change in Accounting Principle
Other income (loss), net		$ 43,000,000.0	6,700,000	13,900,000
Revenues		3,300,000,000	2,700,000,000	2,500,000,000
Interest income on loans held for sale		48,100,000	37,700,000	28,100,000
Labor and related expense		2,200,000,000	1,800,000,000	1,600,000,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs		282,000,000.0	185,400,000	139,700,000
Operating expenses		873,600,000	798,300,000	730,100,000
Depreciation and amortization		181,300,000	174,300,000	166,200,000
Professional and consulting fees		33,300,000	26,400,000	27,200,000
Interest expense, net		32,500,000	31,800,000	21,700,000
Investment Sales | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues				381,300,000
Commercial mortgage origination, net | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues				278,600,000
Capital Markets
New Accounting Pronouncements or Change in Accounting Principle
Revenues		$ 1,047,229,000	$ 774,186,000	659,896,000
Capital Markets | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues				$ 659,900,000