Revenue - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 139,473	$ 125,032
Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	37,774	27,160
Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,121	25,183
Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	14,288	13,288
Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	12,558	9,124
U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	11,524	8,840
UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,055	5,486
Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,765	5,674
Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,613	8,483
Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,376	3,734
Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,827	4,558
Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	13,572	13,502
Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	51,818	51,777
Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	27,632	24,669
Sales Enablement [Member]
Disaggregation of Revenue [Line Items]
Revenue	37,164	23,850
Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	22,859	24,736
Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	100,667	89,621
Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	33,912	33,878
Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	11,276	7,359
Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(6,382)	(5,826)
Workforce Excellence [Member]
Disaggregation of Revenue [Line Items]
Revenue	79,450	76,446
Workforce Excellence [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,693	2,914
Workforce Excellence [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	18,627	22,116
Workforce Excellence [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,978	9,176
Workforce Excellence [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	11,375	7,794
Workforce Excellence [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	9,616	6,518
Workforce Excellence [Member] | UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,055	5,486
Workforce Excellence [Member] | Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,461	3,621
Workforce Excellence [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,452	7,804
Workforce Excellence [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,122	3,683
Workforce Excellence [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,712	1,874
Workforce Excellence [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,359	5,460
Workforce Excellence [Member] | Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	51,818	51,777
Workforce Excellence [Member] | Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	27,632	24,669
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	54,685	48,700
Workforce Excellence [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	22,229	24,634
Workforce Excellence [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,142	7,287
Workforce Excellence [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(3,606)	(4,175)
Business Transformation Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	60,023	48,586
Business Transformation Services [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	36,081	24,246
Business Transformation Services [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,494	3,067
Business Transformation Services [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,310	4,112
Business Transformation Services [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,183	1,330
Business Transformation Services [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,908	2,322
Business Transformation Services [Member] | UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Business Transformation Services [Member] | Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,304	2,053
Business Transformation Services [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,161	679
Business Transformation Services [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	254	51
Business Transformation Services [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,115	2,684
Business Transformation Services [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,213	8,042
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	37,164	23,850
Business Transformation Services [Member] | Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	22,859	24,736
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	45,982	40,921
Business Transformation Services [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	11,683	9,244
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,134	72
Business Transformation Services [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ (2,776)	$ (1,651)