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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, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 202,252	$ 138,361	$ 138,524
Impairment				(59,478)	(7,246)	0
Foreign currency translation				(4,913)	1,693	(163)
Goodwill, ending balance				137,861	202,252	138,361
Goodwill, gross				204,585	209,498		$ 138,524
Accumulated impairment losses				(66,724)	(7,246)		0
Atreus
Goodwill [Roll Forward]
Acquired goodwill					62,371
Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill			$ 7,100		7,073
Executive Search
Goodwill [Roll Forward]
Goodwill, gross				92,203	93,234
On-Demand Talent
Goodwill [Roll Forward]
Goodwill, beginning balance				109,018	45,529	45,529
Impairment				(58,015)	0
Foreign currency translation				(3,882)	1,118	0
Goodwill, ending balance				47,121	109,018	45,529
Goodwill, gross				105,136	109,018		45,529
Accumulated impairment losses				(58,015)			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				0	(7,246)
Foreign currency translation				0	173	0
Goodwill, ending balance				0	0	0
Goodwill, gross				7,246	7,246		0
Accumulated impairment losses				(7,246)			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				91,740	91,383	91,463
Impairment				0	0
Foreign currency translation				(1,000)	357	(80)
Goodwill, ending balance				90,740	91,740	91,383
Goodwill, gross				90,740	91,740		91,463
Accumulated impairment losses				0			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				1,494	1,449	1,532
Impairment				(1,463)	0
Foreign currency translation				(31)	45	(83)
Goodwill, ending balance				0	1,494	1,449
Goodwill, gross				1,463	1,494		1,532
Accumulated impairment losses				(1,463)			0
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	0
Foreign currency translation					0	0
Goodwill, ending balance				0	0	$ 0
Goodwill, gross				0	0		0
Accumulated impairment losses				$ 0			$ 0
Asia Pacific \| Executive Search \| Atreus
Goodwill [Roll Forward]
Acquired goodwill					0
Asia Pacific \| Executive Search \| Businessfourzero
Goodwill [Roll Forward]
Acquired goodwill					$ 0