Goodwill and Other Intangible Assets - Summary of Other Intangible Assets Net by Segment (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	$ 1,730,000	$ 2,216,000
Goodwill	122,070,000	$ 122,092,000
Executive Search [Member]
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	1,730,000
Executive Search [Member] | Americas [Member]
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	13,000
Goodwill	88,547,000
Executive Search [Member] | Europe [Member]
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	1,645,000
Goodwill	24,782,000
Executive Search [Member] | Asia Pacific [Member]
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	72,000
Goodwill	8,741,000
Heidrick Consulting [Domain]
Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	0
Goodwill	$ 0