Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Goodwill [Roll Forward]
Goodwill beginning of period	$ 1,227,593,000
Foreign currency translation adjustment and other	4,176,000
Goodwill end of period	1,231,769,000
Corporate Finance & Restructuring
Goodwill [Roll Forward]
Goodwill beginning of period	516,500,000
Foreign currency translation adjustment and other	(282,000)
Goodwill end of period	516,218,000
Accumulated impairment loss	0	$ 0
Forensic and Litigation Consulting
Goodwill [Roll Forward]
Goodwill beginning of period	234,872,000
Foreign currency translation adjustment and other	1,332,000
Goodwill end of period	236,204,000
Accumulated impairment loss	0	0
Economic Consulting
Goodwill [Roll Forward]
Goodwill beginning of period	268,055,000
Foreign currency translation adjustment and other	262,000
Goodwill end of period	268,317,000
Accumulated impairment loss	0	0
Technology
Goodwill [Roll Forward]
Goodwill beginning of period	96,727,000
Foreign currency translation adjustment and other	63,000
Goodwill end of period	96,790,000
Accumulated impairment loss	0	0
Strategic Communications
Goodwill [Roll Forward]
Goodwill beginning of period	111,439,000
Foreign currency translation adjustment and other	2,801,000
Goodwill end of period	114,240,000
Accumulated impairment loss	194,100,000	194,100,000
Goodwill	$ 308,300,000	$ 305,600,000