Segment Information - Revenue, Operating Income, Depreciation and Amortization, and Capital Expenditures, by Segment (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	$ 706,924	$ 716,023	$ 621,400
Revenue:
Reimbursements Revenue	18,690	19,632	18,656
Total revenue	725,614	735,655	640,056
Operating income (loss)
Operating (loss) income	63,511	68,857	(26,523)
Depreciation and amortization
Depreciation and amortization	10,371	12,522	14,774
Capital expenditures
Capital expenditures	$ 3,352	6,185	15,686
Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments	4
Operating income (loss)
Operating (loss) income	$ 98,950	105,109	13,519
Depreciation and amortization
Depreciation and amortization	9,539	11,563	13,786
Capital expenditures
Capital expenditures	3,027	5,179	12,388
Corporate, Non-Segment [Member]
Operating income (loss)
Operating (loss) income	(35,439)	(36,252)	(40,042)
Depreciation and amortization
Depreciation and amortization	832	959	988
Capital expenditures
Capital expenditures	325	1,006	3,298
Executive Search [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	646,352	652,891	552,044
Operating income (loss)
Operating (loss) income	117,449	118,728	75,887
Depreciation and amortization
Depreciation and amortization	8,460	9,986	9,687
Capital expenditures
Capital expenditures	2,486	4,598	11,216
Heidrick Consulting [Domain] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	60,572	63,132	69,356
Operating income (loss)
Operating (loss) income	(18,499)	(13,619)	(62,368)
Depreciation and amortization
Depreciation and amortization	1,079	1,577	4,099
Capital expenditures
Capital expenditures	541	581	1,172
Americas [Member] | Executive Search [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	415,455	405,267	339,793
Operating income (loss)
Operating (loss) income	100,833	96,880	75,337
Depreciation and amortization
Depreciation and amortization	4,204	4,605	4,794
Capital expenditures
Capital expenditures	1,121	601	7,123
Europe [Member] | Executive Search [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	135,070	145,348	125,346
Operating income (loss)
Operating (loss) income	3,026	5,849	13
Depreciation and amortization
Depreciation and amortization	2,784	3,735	3,328
Capital expenditures
Capital expenditures	1,070	3,557	1,460
Asia Pacific [Member] | Executive Search [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net of Reimbursements	95,827	102,276	86,905
Operating income (loss)
Operating (loss) income	13,590	15,999	537
Depreciation and amortization
Depreciation and amortization	1,472	1,646	1,565
Capital expenditures
Capital expenditures	$ 295	$ 440	$ 2,633