Goodwill and Intangible Assets - Summary of Changes in Carrying Amounts of Goodwill by Operating Segment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill beginning of period	$ 1,232,791,000	$ 1,234,879,000
Acquisitions	11,332,000	5,493,000
Foreign currency translation adjustment and other	(16,530,000)	(7,581,000)
Goodwill end of period	1,227,593,000	1,232,791,000
Corporate Finance
Goodwill [Roll Forward]
Goodwill beginning of period	501,046,000	506,072,000
Acquisitions	11,332,000	0
Foreign currency translation adjustment and other	4,122,000	(5,026,000)
Goodwill end of period	516,500,000	501,046,000
Accumulated impairment loss	0	0	$ 0
FLC
Goodwill [Roll Forward]
Goodwill beginning of period	237,929,000	233,374,000
Acquisitions	0	5,493,000
Foreign currency translation adjustment and other	(3,057,000)	(938,000)
Goodwill end of period	234,872,000	237,929,000
Accumulated impairment loss	0	0	0
Economic Consulting
Goodwill [Roll Forward]
Goodwill beginning of period	268,858,000	269,087,000
Acquisitions	0	0
Foreign currency translation adjustment and other	(803,000)	(229,000)
Goodwill end of period	268,055,000	268,858,000
Accumulated impairment loss	0	0	0
Technology
Goodwill [Roll Forward]
Goodwill beginning of period	96,811,000	96,821,000
Acquisitions	0	0
Foreign currency translation adjustment and other	(84,000)	(10,000)
Goodwill end of period	96,727,000	96,811,000
Accumulated impairment loss	0	0	0
Strategic Communications
Goodwill [Roll Forward]
Goodwill beginning of period	128,147,000	129,525,000
Acquisitions	0	0
Foreign currency translation adjustment and other	(16,708,000)	(1,378,000)
Goodwill end of period	111,439,000	128,147,000
Accumulated impairment loss	194,100,000	194,100,000	194,100,000
Goodwill	$ 305,600,000	$ 322,300,000	$ 323,700,000