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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 893,261	$ 775,865	$ 2,564,558	$ 2,254,477
Adjusted Segment EBITDA	145,657	128,767	397,382	362,974
Corporate Finance
Segment Reporting Information [Line Items]
Revenues	347,560	282,029	981,124	841,804
Adjusted Segment EBITDA	68,094	53,519	165,450	165,683
FLC
Segment Reporting Information [Line Items]
Revenues	166,137	143,289	488,636	432,054
Adjusted Segment EBITDA	21,480	16,175	68,861	46,464
Economic Consulting
Segment Reporting Information [Line Items]
Revenues	193,866	193,183	565,283	523,201
Adjusted Segment EBITDA	27,756	32,913	77,472	75,754
Technology
Segment Reporting Information [Line Items]
Revenues	98,860	84,915	286,922	243,181
Adjusted Segment EBITDA	14,873	13,213	50,326	34,940
Strategic Communications
Segment Reporting Information [Line Items]
Revenues	86,838	72,449	242,593	214,237
Adjusted Segment EBITDA	$ 13,454	$ 12,947	$ 35,273	$ 40,133