Restructuring and Related Activities (Details) - USD ($)	3 Months Ended		6 Months Ended		21 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 8,863,000		$ 8,863,000		$ 8,863,000	$ 23,265,000
Restructuring Charges	3,193,000	$ 0	7,054,000	$ 0	59,425,000
Payments for Restructuring			(13,999,000)
Restructuring Reserve, Settled without Cash			(7,459,000)
Restructuring Reserve, Foreign Currency Translation Gain (Loss)			2,000
Other Restructuring Costs			0
Americas
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	3,100,000		6,800,000
Europe
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	(100,000)		(100,000)
Asia Pacific
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(100,000)
Employee-related Liabilities, Current
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	4,900,000		4,900,000		4,900,000	7,200,000
Accrued Salaries and Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	3,600,000		3,600,000		3,600,000	11,300,000
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	2,000,000.0		2,000,000.0		2,000,000.0
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	1,000,000.0		1,000,000.0		1,000,000.0
Heidrick Consulting
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	300,000		600,000
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	8,792,000		8,792,000		8,792,000	22,312,000
Restructuring Charges	96,000		290,000		32,489,000
Payments for Restructuring			(13,276,000)
Restructuring Reserve, Settled without Cash			44,000
Restructuring Reserve, Foreign Currency Translation Gain (Loss)			2,000
Other Restructuring Costs			0
Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	71,000		71,000		71,000	953,000
Restructuring Charges	(3,289,000)		(7,331,000)		26,241,000
Payments for Restructuring			(710,000)
Restructuring Reserve, Settled without Cash			(7,503,000)
Restructuring Reserve, Foreign Currency Translation Gain (Loss)			0
Other Restructuring Costs			0
Other Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 0		0		0	$ 0
Restructuring Charges			(13,000)		$ 695,000
Payments for Restructuring			(13,000)
Restructuring Reserve, Settled without Cash			0
Restructuring Reserve, Foreign Currency Translation Gain (Loss)			0
Other Restructuring Costs			$ 0