Segment Reporting - Revenues and Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 864,591	$ 754,992	$ 1,671,297	$ 1,478,612
Adjusted Segment EBITDA	138,981	113,140	251,727	234,208
Corporate Finance
Segment Reporting Information [Line Items]
Revenues	300,449	277,067	600,436	530,396
Adjusted Segment EBITDA	50,028	54,950	105,048	108,490
FLC
Segment Reporting Information [Line Items]
Revenues	182,223	164,248	355,627	318,144
Adjusted Segment EBITDA	21,080	16,707	39,691	33,964
Economic Consulting
Segment Reporting Information [Line Items]
Revenues	201,822	164,041	371,417	330,018
Adjusted Segment EBITDA	35,523	21,646	49,716	42,841
Technology
Segment Reporting Information [Line Items]
Revenues	97,444	77,782	188,062	158,266
Adjusted Segment EBITDA	20,087	8,365	35,453	21,728
Strategic Communications
Segment Reporting Information [Line Items]
Revenues	82,653	71,854	155,755	141,788
Adjusted Segment EBITDA	$ 12,263	$ 11,472	$ 21,819	$ 27,185