Revenue - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 128,281	$ 139,473
Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	32,155	37,774
Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	20,627	21,121
Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	12,116	14,288
Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,448	12,558
U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	12,788	11,524
UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,267	4,043
Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,744	5,765
Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	9,313	7,613
Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,840	4,376
Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,322	6,827
Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	14,661	13,584
Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	42,498	44,642
Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	31,880	36,836
Sales Enablement [Member]
Disaggregation of Revenue [Line Items]
Revenue	32,488	35,551
Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,415	22,444
Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	93,412	100,284
Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	33,833	34,295
Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	10,184	11,276
Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(9,148)	(6,382)
Workforce Excellence [Member]
Disaggregation of Revenue [Line Items]
Revenue	74,378	81,478
Workforce Excellence [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,453	3,598
Workforce Excellence [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	19,156	19,206
Workforce Excellence [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	9,158	9,270
Workforce Excellence [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,275	11,530
Workforce Excellence [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	11,206	9,795
Workforce Excellence [Member] | UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Workforce Excellence [Member] | Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,115	5,306
Workforce Excellence [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,296	7,510
Workforce Excellence [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,623	4,130
Workforce Excellence [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,108	4,894
Workforce Excellence [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,988	6,239
Workforce Excellence [Member] | Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	42,498	44,642
Workforce Excellence [Member] | Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	31,880	36,836
Workforce Excellence [Member] | Sales Enablement [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Workforce Excellence [Member] | Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Workforce Excellence [Member] | Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	56,563	59,664
Workforce Excellence [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	17,672	19,278
Workforce Excellence [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,445	6,142
Workforce Excellence [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(5,302)	(3,606)
Business Transformation Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	53,903	57,995
Business Transformation Services [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	29,702	34,176
Business Transformation Services [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,471	1,915
Business Transformation Services [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,958	5,018
Business Transformation Services [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,173	1,028
Business Transformation Services [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,582	1,729
Business Transformation Services [Member] | UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,267	4,043
Business Transformation Services [Member] | Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	629	459
Business Transformation Services [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,017	103
Business Transformation Services [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	217	246
Business Transformation Services [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,214	1,933
Business Transformation Services [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,673	7,345
Business Transformation Services [Member] | Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Business Transformation Services [Member] | Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Business Transformation Services [Member] | Sales Enablement [Member]
Disaggregation of Revenue [Line Items]
Revenue	32,488	35,551
Business Transformation Services [Member] | Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,415	22,444
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	36,849	40,620
Business Transformation Services [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	16,161	15,017
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,739	5,134
Business Transformation Services [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ (3,846)	$ (2,776)