Segment Reporting - Revenues and Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 723,620	$ 686,277
Adjusted Segment EBITDA	121,067	125,446
Corporate Finance
Segment Reporting Information [Line Items]
Revenues	253,329	226,203
Adjusted Segment EBITDA	53,539	37,439
FLC
Segment Reporting Information [Line Items]
Revenues	153,896	150,821
Adjusted Segment EBITDA	17,257	29,432
Economic Consulting
Segment Reporting Information [Line Items]
Revenues	165,977	169,273
Adjusted Segment EBITDA	21,195	26,579
Technology
Segment Reporting Information [Line Items]
Revenues	80,484	79,459
Adjusted Segment EBITDA	13,363	21,598
Strategic Communications
Segment Reporting Information [Line Items]
Revenues	69,934	60,521
Adjusted Segment EBITDA	$ 15,713	$ 10,398