Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Provision (reversal) for expected credit losses		$ (2,200,000)	$ 900,000	$ 1,700,000
Guaranty liabilities	$ 26,315,000	26,315,000	28,551,000	27,729,000
Allowance for doubtful accounts, period increase (decrease)		(5,100,000)	(1,400,000)	4,200,000
Allowance for doubtful accounts	14,400,000	14,400,000	19,500,000
Allowance for credit loss	8,800,000	8,800,000	9,400,000
Revenues		$ 2,738,502,000	2,470,368,000	2,705,527,000
Number of reportable segments | segment		1
Interest income on loans held for sale		$ 37,716,000	28,068,000	26,821,000
Labor and related expense		1,783,798,000	1,628,885,000	1,693,096,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs		185,398,000	139,747,000	138,312,000
Depreciation and amortization		174,299,000	166,221,000	165,816,000
Professional and consulting fees		26,446,000	27,204,000	28,502,000
Interest expense, net		(31,768,000)	(21,737,000)	(30,970,000)
Other income (loss), net		6,677,000	13,854,000	(97,701,000)
Total assets	$ 4,710,120,000	4,710,120,000	4,471,575,000
Impairment of intangible assets		$ 0	0	0
Percentage to preferred units	0.6875%	2.75%
Reportable Segment
New Accounting Pronouncements or Change in Accounting Principle
Revenues		$ 2,700,000,000
Interest income on loans held for sale		37,700,000
Labor and related expense		1,800,000,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs		185,400,000
Operating expenses		798,300,000
Depreciation and amortization		174,300,000
Professional and consulting fees		26,400,000
Interest expense, net		31,800,000
Other income (loss), net		6,700,000
Capital markets
New Accounting Pronouncements or Change in Accounting Principle
Revenues		774,186,000	659,896,000	964,168,000
Capital markets | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues			659,900,000	964,200,000
Investment sales | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues		381,300,000	606,400,000
Commercial mortgage origination, net
New Accounting Pronouncements or Change in Accounting Principle
Revenues				$ 964,168,000
Commercial mortgage origination, net | Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Revenues		$ 278,600,000	$ 357,800,000