SEGMENT AND GEOGRAPHIC DATA - Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) Segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | Segment	3
Revenue, from external customers	$ 34,461	$ 24,131
Inter-segment revenue	0	0
Revenue	34,461	24,131
Adjusted net revenue, from external customers	12,718	9,798
Inter-segment adjusted net revenue	0	0
Total adjusted net revenue	12,718	9,798
EBITDA (loss)	75	(459)
Depreciation and amortization	(110)	(24)
Intercompany interest (expense) income, net	0	0
Intercompany interest (expense) income, net	10	79
Loss before provision for income taxes	(25)	(404)
Provision for income taxes	178	107
Accounts receivable, net	17,118	12,778	$ 13,445
Long-lived assets, net of accumulated depreciation and amortization	3,533	164
Total assets	46,981	41,312	$ 45,386
Inter-Segment Elimination
Segment Reporting Information [Line Items]
Revenue, from external customers		0
Inter-segment revenue		(6)
Revenue		(6)
Adjusted net revenue, from external customers		0
Inter-segment adjusted net revenue		0
Total adjusted net revenue		0
EBITDA (loss)		0
Depreciation and amortization		0
Intercompany interest (expense) income, net		0
Intercompany interest (expense) income, net		0
Loss before provision for income taxes		0
Provision for income taxes		0
Accounts receivable, net		0
Long-lived assets, net of accumulated depreciation and amortization		0
Total assets		0
Hudson Americas | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers	4,561	3,188
Inter-segment revenue	0	0
Revenue	4,561	3,188
Adjusted net revenue, from external customers	4,209	2,860
Inter-segment adjusted net revenue	0	0
Total adjusted net revenue	4,209	2,860
EBITDA (loss)	(278)	(60)
Depreciation and amortization	(86)	(5)
Intercompany interest (expense) income, net	0	0
Intercompany interest (expense) income, net	0	0
Loss before provision for income taxes	(364)	(65)
Provision for income taxes	9	9
Accounts receivable, net	3,456	2,857
Long-lived assets, net of accumulated depreciation and amortization	3,432	29
Total assets	8,916	3,998
Hudson Asia Pacific | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers	25,340	16,951
Inter-segment revenue	0	6
Revenue	25,340	16,957
Adjusted net revenue, from external customers	5,758	4,511
Inter-segment adjusted net revenue	0	6
Total adjusted net revenue	5,758	4,517
EBITDA (loss)	762	337
Depreciation and amortization	(14)	(12)
Intercompany interest (expense) income, net	(85)	(86)
Intercompany interest (expense) income, net	1	0
Loss before provision for income taxes	664	239
Provision for income taxes	194	64
Accounts receivable, net	9,883	7,172
Long-lived assets, net of accumulated depreciation and amortization	63	90
Total assets	16,478	11,568
Hudson Europe | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers	4,560	3,992
Inter-segment revenue	0	0
Revenue	4,560	3,992
Adjusted net revenue, from external customers	2,751	2,427
Inter-segment adjusted net revenue	0	(6)
Total adjusted net revenue	2,751	2,421
EBITDA (loss)	70	63
Depreciation and amortization	(9)	(6)
Intercompany interest (expense) income, net	0	0
Intercompany interest (expense) income, net	0	0
Loss before provision for income taxes	61	57
Provision for income taxes	17	10
Accounts receivable, net	3,771	2,715
Long-lived assets, net of accumulated depreciation and amortization	34	35
Total assets	8,132	6,234
Corporate Segment | Operating Segments
Segment Reporting Information [Line Items]
Revenue, from external customers	0	0
Inter-segment revenue	0	0
Revenue	0	0
Adjusted net revenue, from external customers	0	0
Inter-segment adjusted net revenue	0	0
Total adjusted net revenue	0	0
EBITDA (loss)	(479)	(799)
Depreciation and amortization	(1)	(1)
Intercompany interest (expense) income, net	85	86
Intercompany interest (expense) income, net	9	79
Loss before provision for income taxes	(386)	(635)
Provision for income taxes	(42)	24
Accounts receivable, net	8	34
Long-lived assets, net of accumulated depreciation and amortization	4	10
Total assets	$ 13,455	$ 19,512