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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 754,992	$ 711,486	$ 1,478,612	$ 1,397,763
Adjusted Segment EBITDA	113,140	120,894	234,208	246,340
Corporate Finance
Segment Reporting Information [Line Items]
Revenues	277,067	230,971	530,396	457,174
Adjusted Segment EBITDA	54,950	40,174	108,490	77,613
FLC
Segment Reporting Information [Line Items]
Revenues	164,248	150,746	318,144	301,567
Adjusted Segment EBITDA	16,707	18,002	33,964	47,434
Economic Consulting
Segment Reporting Information [Line Items]
Revenues	164,041	183,306	330,018	352,579
Adjusted Segment EBITDA	21,646	30,699	42,841	57,278
Technology
Segment Reporting Information [Line Items]
Revenues	77,782	78,646	158,266	158,105
Adjusted Segment EBITDA	8,365	18,518	21,728	40,116
Strategic Communications
Segment Reporting Information [Line Items]
Revenues	71,854	67,817	141,788	128,338
Adjusted Segment EBITDA	$ 11,472	$ 13,501	$ 27,185	$ 23,899