Segment Reporting - Revenues and Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 775,865	$ 702,228	$ 2,254,477	$ 2,099,991
Adjusted Segment EBITDA	128,767	125,496	362,974	371,836
Corporate Finance
Segment Reporting Information [Line Items]
Revenues	265,370	250,321	795,766	707,495
Adjusted Segment EBITDA	51,532	55,635	160,021	133,248
FLC
Segment Reporting Information [Line Items]
Revenues	159,948	145,264	478,092	446,831
Adjusted Segment EBITDA	18,162	16,620	52,126	64,054
Economic Consulting
Segment Reporting Information [Line Items]
Revenues	193,183	172,543	523,201	525,122
Adjusted Segment EBITDA	32,913	29,917	75,754	87,195
Technology
Segment Reporting Information [Line Items]
Revenues	84,915	64,657	243,181	222,762
Adjusted Segment EBITDA	13,213	7,835	34,940	47,951
Strategic Communications
Segment Reporting Information [Line Items]
Revenues	72,449	69,443	214,237	197,781
Adjusted Segment EBITDA	$ 12,947	$ 15,489	$ 40,133	$ 39,388