Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill by Operating Segment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Goodwill [Roll Forward]
Goodwill beginning of period	$ 1,226,556,000	$ 1,234,569,000
Foreign currency translation adjustment	16,221,000	(8,013,000)
Goodwill end of period	1,242,777,000	1,226,556,000
Corporate Finance
Goodwill [Roll Forward]
Goodwill beginning of period	535,328,000	540,991,000
Foreign currency translation adjustment	7,915,000	(5,663,000)
Goodwill end of period	543,243,000	535,328,000
Accumulated impairment loss	0	0	$ 0
FLC
Goodwill [Roll Forward]
Goodwill beginning of period	212,367,000	213,415,000
Foreign currency translation adjustment	2,807,000	(1,048,000)
Goodwill end of period	215,174,000	212,367,000
Accumulated impairment loss	0	0	0
Economic Consulting
Goodwill [Roll Forward]
Goodwill beginning of period	268,294,000	268,482,000
Foreign currency translation adjustment	626,000	(188,000)
Goodwill end of period	268,920,000	268,294,000
Accumulated impairment loss	0	0	0
Technology
Goodwill [Roll Forward]
Goodwill beginning of period	96,784,000	96,802,000
Foreign currency translation adjustment	103,000	(18,000)
Goodwill end of period	96,887,000	96,784,000
Accumulated impairment loss	0	0	0
Strategic Communications
Goodwill [Roll Forward]
Goodwill beginning of period	113,783,000	114,879,000
Foreign currency translation adjustment	4,770,000	(1,096,000)
Goodwill end of period	118,553,000	113,783,000
Accumulated impairment loss	194,100,000	194,100,000	194,100,000
Goodwill	$ 312,700,000	$ 307,900,000	$ 309,000,000.0