SEGMENT AND GEOGRAPHIC DATA - Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Segment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | Segment			3
Revenue, from external customers		$ 25,413	$ 119,145	$ 74,117
Inter-segment revenue		0	0	0
Revenue	$ 45,010	25,413	119,145	74,117
Adjusted net revenue, from external customers		9,070	45,840	27,798
Inter-segment adjusted net revenue		0	0	0
Total adjusted net revenue	18,031	9,070	45,840	27,798
EBITDA (loss)	1,511	(981)	1,957	(1,962)
Depreciation and amortization	(117)	(25)	(340)	(73)
Intercompany (expense) interest income, net	0	0	0	0
Interest income, net	8	14	27	133
Net income (loss) before income taxes	1,402	(992)	1,644	(1,902)
Provision for (benefit from) income taxes	(92)	165	475	538
Accounts receivable, net	20,970	11,916	20,970	11,916	$ 13,445
Long-lived assets, net of accumulated depreciation and amortization	3,407	132	3,407	132
Total assets	54,025	43,995	54,025	43,995	$ 45,386
Inter-Segment Elimination
Segment Reporting Information [Line Items]
Revenue, from external customers		0	0	0
Inter-segment revenue		(97)	(15)	(103)
Revenue	0	(97)	(15)	(103)
Adjusted net revenue, from external customers		0	0	0
Inter-segment adjusted net revenue		0	0	0
Total adjusted net revenue	0	0	0	0
EBITDA (loss)	0	0	0	0
Depreciation and amortization	0	0	0	0
Intercompany (expense) interest income, net	0	0	0	0
Interest income, net	0	0	0	0
Net income (loss) before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Accounts receivable, net	0	0	0	0
Long-lived assets, net of accumulated depreciation and amortization	0	0	0	0
Total assets	0	0	0	0
Hudson Americas | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers		1,934	17,350	7,328
Inter-segment revenue		97	0	97
Revenue	7,423	2,031	17,350	7,425
Adjusted net revenue, from external customers		1,678	16,232	6,431
Inter-segment adjusted net revenue		97	(15)	97
Total adjusted net revenue	7,030	1,775	16,217	6,528
EBITDA (loss)	604	(789)	153	(1,767)
Depreciation and amortization	(91)	(5)	(264)	(14)
Intercompany (expense) interest income, net	0	0	0	0
Interest income, net	0	(4)	0	(6)
Net income (loss) before income taxes	513	(798)	(111)	(1,787)
Provision for (benefit from) income taxes	(596)	8	(579)	25
Accounts receivable, net	5,411	1,353	5,411	1,353
Long-lived assets, net of accumulated depreciation and amortization	3,305	21	3,305	21
Total assets	10,798	3,809	10,798	3,809
Hudson Asia Pacific | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers		19,877	86,414	55,661
Inter-segment revenue		0	15	6
Revenue	32,273	19,877	86,429	55,667
Adjusted net revenue, from external customers		5,002	20,563	14,331
Inter-segment adjusted net revenue		0	15	6
Total adjusted net revenue	7,925	5,002	20,578	14,337
EBITDA (loss)	1,809	517	3,574	1,879
Depreciation and amortization	(19)	(13)	(50)	(38)
Intercompany (expense) interest income, net	(81)	(81)	(252)	(240)
Interest income, net	0	2	2	2
Net income (loss) before income taxes	1,709	425	3,274	1,603
Provision for (benefit from) income taxes	438	115	875	452
Accounts receivable, net	10,707	7,558	10,707	7,558
Long-lived assets, net of accumulated depreciation and amortization	65	73	65	73
Total assets	20,461	14,022	20,461	14,022
Hudson Europe | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers		3,602	15,381	11,128
Inter-segment revenue		0	0	0
Revenue	5,314	3,602	15,381	11,128
Adjusted net revenue, from external customers		2,390	9,045	7,036
Inter-segment adjusted net revenue		(97)	0	(103)
Total adjusted net revenue	3,076	2,293	9,045	6,933
EBITDA (loss)	111	(40)	657	323
Depreciation and amortization	(6)	(6)	(23)	(17)
Intercompany (expense) interest income, net	0	0	0	0
Interest income, net	0	0	0	0
Net income (loss) before income taxes	105	(46)	634	306
Provision for (benefit from) income taxes	24	1	164	4
Accounts receivable, net	4,852	3,005	4,852	3,005
Long-lived assets, net of accumulated depreciation and amortization	33	32	33	32
Total assets	8,833	7,597	8,833	7,597
Corporate Segment | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers		0	0	0
Inter-segment revenue		0	0	0
Revenue	0	0	0	0
Adjusted net revenue, from external customers		0	0	0
Inter-segment adjusted net revenue		0	0	0
Total adjusted net revenue	0	0	0	0
EBITDA (loss)	(1,013)	(669)	(2,427)	(2,397)
Depreciation and amortization	(1)	(1)	(3)	(4)
Intercompany (expense) interest income, net	81	81	252	240
Interest income, net	8	16	25	137
Net income (loss) before income taxes	(925)	(573)	(2,153)	(2,024)
Provision for (benefit from) income taxes	42	41	15	57
Accounts receivable, net	0	0	0	0
Long-lived assets, net of accumulated depreciation and amortization	4	6	4	6
Total assets	$ 13,933	$ 18,567	$ 13,933	$ 18,567