SEGMENT AND GEOGRAPHIC DATA Segment Information (Details) $ in Thousands	3 Months Ended			6 Months Ended		9 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2019 USD ($) segments	Jun. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segments				3
Revenue from external customers	$ 26,414			$ 42,601
Segment Reporting Information, Revenue Intersegment	0			0
Revenue	26,414	$ 17,015	$ 17,015	42,601	$ 33,230	$ 33,230
Gross margin, from external customer	11,659			21,055
Segment Reporting Information, Intersegment Gross Margin	0			0
Gross profit	11,659	10,801		21,055	20,955
EBITDA (loss)	(862)	(1,302)		(2,863)	(4,027)
Depreciation and amortization	21	2		39	2
Segment Reporting Information, Intersegment Interest Income (Expense), Net	0	0		0	0
Interest income, net	125	60		438	60
Loss from continuing operations before provision for income taxes	(758)	(1,244)		(2,464)	(3,969)
Accounts receivable, net	14,382	14,201		14,382	14,201		$ 9,893
Long-lived assets, net of accumulated depreciation and amortization (b)			$ 5			$ 5		$ 811
Total assets	46,133	54,522		46,133	54,522		$ 53,179
Operating Segments | Hudson Americas
Segment Reporting Information [Line Items]
Revenue from external customers	3,982			7,122
Segment Reporting Information, Revenue Intersegment	28			63
Revenue	4,010	3,509		7,185	7,209
Gross margin, from external customer	3,591			6,353
Segment Reporting Information, Intersegment Gross Margin	26			61
Gross profit	3,617	2,923		6,414	6,046
EBITDA (loss)	428	(76)		14	215
Depreciation and amortization	4	0		9	0
Segment Reporting Information, Intersegment Interest Income (Expense), Net	0	0		0	0
Interest income, net	0	0		0	0
Loss from continuing operations before provision for income taxes	424	(76)		5	215
Accounts receivable, net	3,336	2,605		3,336	2,605
Total assets	4,742	4,618		4,742	4,618
Operating Segments | Hudson Asia Pacific
Segment Reporting Information [Line Items]
Revenue from external customers	17,454			26,133
Segment Reporting Information, Revenue Intersegment	0
Revenue	17,454	9,600		26,133	18,425
Gross margin, from external customer	5,420			10,010
Segment Reporting Information, Intersegment Gross Margin	(28)			(58)
Gross profit	5,392	5,759		9,952	10,682
EBITDA (loss)	362	508		314	1,052
Depreciation and amortization	10	0		15	0
Segment Reporting Information, Intersegment Interest Income (Expense), Net	(100)	(108)		(201)	(108)
Interest income, net	0	0		0	0
Loss from continuing operations before provision for income taxes	252	400		98	944
Accounts receivable, net	8,106	6,787		8,106	6,787
Total assets	11,654	9,863		11,654	9,863
Operating Segments | Hudson Europe
Segment Reporting Information [Line Items]
Revenue from external customers	4,978			9,346
Segment Reporting Information, Revenue Intersegment	2			3
Revenue	4,980	3,906		9,349	7,596
Gross margin, from external customer	2,648			4,692
Segment Reporting Information, Intersegment Gross Margin	3			3
Gross profit	2,651	2,119		4,695	4,227
EBITDA (loss)	31	34		(317)	45
Depreciation and amortization	6	2		13	2
Segment Reporting Information, Intersegment Interest Income (Expense), Net	0	0		0	0
Interest income, net	0	0		0	0
Loss from continuing operations before provision for income taxes	25	32		(330)	43
Accounts receivable, net	3,005	4,803		3,005	4,803
Total assets	6,674	8,643		6,674	8,643
Corporate
Segment Reporting Information [Line Items]
Revenue from external customers	0			0
Segment Reporting Information, Revenue Intersegment	0			0
Revenue	0	0		0	0
Gross margin, from external customer	0			0
Segment Reporting Information, Intersegment Gross Margin	0			0
Gross profit	0	0		0	0
EBITDA (loss)	(1,683)	(1,768)		(2,874)	(5,339)
Depreciation and amortization	1	0		2	0
Segment Reporting Information, Intersegment Interest Income (Expense), Net	100	108		201	108
Interest income, net	125	60		438	60
Loss from continuing operations before provision for income taxes	(1,459)	(1,600)		(2,237)	(5,171)
Accounts receivable, net	(65)	6		(65)	6
Total assets	23,063	31,398		23,063	31,398
Inter-Segment Elimination
Segment Reporting Information [Line Items]
Revenue from external customers	0			0
Segment Reporting Information, Revenue Intersegment	(30)			(66)
Revenue	(30)	0		(66)	0
Gross margin, from external customer	0			0
Segment Reporting Information, Intersegment Gross Margin	(1)			(6)
Gross profit	(1)	0		(6)	0
EBITDA (loss)	0			0
Depreciation and amortization	0	0		0	0
Segment Reporting Information, Intersegment Interest Income (Expense), Net	0	0		0	0
Interest income, net	0	0		0	0
Loss from continuing operations before provision for income taxes	0	0		0	0
Accounts receivable, net	0	0		0	0
Total assets	$ 0	$ 0		$ 0	$ 0