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Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Apr. 30, 2023	Feb. 28, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 138,361	$ 138,524	$ 91,643
Acquired goodwill				69,444
Impairment				(7,246)
Foreign currency translation				1,693	(163)	(180)
Goodwill, ending balance				202,252	138,361	138,524
Goodwill, gross				242,468			$ 124,613
Accumulated impairment losses				(40,216)			(32,970)
BTG
Goodwill [Roll Forward]
Acquired goodwill						45,529
Finland
Goodwill [Roll Forward]
Acquired goodwill						1,532
Atreus
Goodwill [Roll Forward]
Acquired goodwill				62,371
Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill			$ 7,100	7,073
Executive Search
Goodwill [Roll Forward]
Goodwill, beginning balance				92,832
Goodwill, ending balance				93,234	92,832
On-Demand Talent
Goodwill [Roll Forward]
Goodwill, beginning balance				45,529	45,529	0
Impairment				0
Foreign currency translation				1,118	0	0
Goodwill, ending balance				109,018	45,529	45,529
Goodwill, gross				109,018			0
Accumulated impairment losses				0			0
On-Demand Talent \| BTG
Goodwill [Roll Forward]
Acquired goodwill						45,529
On-Demand Talent \| Finland
Goodwill [Roll Forward]
Acquired goodwill						0
On-Demand Talent \| Atreus
Goodwill [Roll Forward]
Acquired goodwill		$ 62,400		62,371
On-Demand Talent \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill				0
Heidrick Consulting
Goodwill [Roll Forward]
Goodwill, beginning balance				0	0	0
Impairment				(7,246)
Foreign currency translation				173	0	0
Goodwill, ending balance				0	0	0
Goodwill, gross				7,246			0
Accumulated impairment losses				(7,246)			0
Heidrick Consulting \| BTG
Goodwill [Roll Forward]
Acquired goodwill						0
Heidrick Consulting \| Finland
Goodwill [Roll Forward]
Acquired goodwill						0
Heidrick Consulting \| Atreus
Goodwill [Roll Forward]
Acquired goodwill				0
Heidrick Consulting \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill	$ 7,100			7,073
Americas \| Executive Search
Goodwill [Roll Forward]
Goodwill, beginning balance				91,383	91,463	91,643
Impairment				0
Foreign currency translation				357	(80)	(180)
Goodwill, ending balance				91,740	91,383	91,463
Goodwill, gross				91,740			91,643
Accumulated impairment losses				0			0
Americas \| Executive Search \| BTG
Goodwill [Roll Forward]
Acquired goodwill						0
Americas \| Executive Search \| Finland
Goodwill [Roll Forward]
Acquired goodwill						0
Americas \| Executive Search \| Atreus
Goodwill [Roll Forward]
Acquired goodwill				0
Americas \| Executive Search \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill				0
Europe \| Executive Search
Goodwill [Roll Forward]
Goodwill, beginning balance				1,449	1,532	0
Impairment				0
Foreign currency translation				45	(83)	0
Goodwill, ending balance				1,494	1,449	1,532
Goodwill, gross				25,969			24,475
Accumulated impairment losses				(24,475)			(24,475)
Europe \| Executive Search \| BTG
Goodwill [Roll Forward]
Acquired goodwill						0
Europe \| Executive Search \| Finland
Goodwill [Roll Forward]
Acquired goodwill						1,532
Europe \| Executive Search \| Atreus
Goodwill [Roll Forward]
Acquired goodwill				0
Europe \| Executive Search \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill				0
Asia Pacific \| Executive Search
Goodwill [Roll Forward]
Goodwill, beginning balance				0	0	0
Impairment				0
Foreign currency translation				0	0	0
Goodwill, ending balance				0	$ 0	0
Goodwill, gross				8,495			8,495
Accumulated impairment losses				(8,495)			$ (8,495)
Asia Pacific \| Executive Search \| BTG
Goodwill [Roll Forward]
Acquired goodwill						0
Asia Pacific \| Executive Search \| Finland
Goodwill [Roll Forward]
Acquired goodwill						$ 0
Asia Pacific \| Executive Search \| Atreus
Goodwill [Roll Forward]
Acquired goodwill				0
Asia Pacific \| Executive Search \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill				$ 0