Revenue - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 125,032	$ 122,446
Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	27,184	27,115
Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	25,173	24,045
Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	13,288	12,536
Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	9,117	10,037
U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,840	8,696
UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,486	6,730
Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,674	6,702
Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,359	6,552
Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,734	4,758
Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,557	4,219
Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	13,620	11,056
Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	48,902	45,329
Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	25,529	26,213
Sales Enablement [Member]
Disaggregation of Revenue [Line Items]
Revenue	23,850	24,617
Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	26,751	26,287
Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	89,622	91,338
Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	33,454	29,344
Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,783	7,242
Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(5,827)	(5,478)
Workforce Excellence [Member]
Disaggregation of Revenue [Line Items]
Revenue	74,431	71,542
Workforce Excellence [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,838	2,258
Workforce Excellence [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,103	18,586
Workforce Excellence [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,679	8,275
Workforce Excellence [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,642	9,050
Workforce Excellence [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,454	6,153
Workforce Excellence [Member] | UK Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,486	6,730
Workforce Excellence [Member] | Information and Communication Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,299	3,980
Workforce Excellence [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,598	5,039
Workforce Excellence [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,683	4,363
Workforce Excellence [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,849	1,724
Workforce Excellence [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,800	5,384
Workforce Excellence [Member] | Managed Learning Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	48,902	45,329
Workforce Excellence [Member] | Engineering and Technical Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	25,529	26,213
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	45,440	44,940
Workforce Excellence [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	24,957	23,591
Workforce Excellence [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,711	7,130
Workforce Excellence [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(3,677)	(4,119)
Business Transformation Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	50,601	50,904
Business Transformation Services [Member] | Automotive Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	24,346	24,857
Business Transformation Services [Member] | Financial and Insurance Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,070	5,459
Business Transformation Services [Member] | Manufacturing Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,609	4,261
Business Transformation Services [Member] | Energy, Oil and Gas Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,475	987
Business Transformation Services [Member] | U.S. Government Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,386	2,543
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	2,375	2,722
Business Transformation Services [Member] | Aerospace Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	761	1,513
Business Transformation Services [Member] | Electronics Semiconductor Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	51	395
Business Transformation Services [Member] | Life Sciences Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,708	2,495
Business Transformation Services [Member] | Other Market Sector [Member]
Disaggregation of Revenue [Line Items]
Revenue	7,820	5,672
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	23,850	24,617
Business Transformation Services [Member] | Organizational Development [Member]
Disaggregation of Revenue [Line Items]
Revenue	26,751	26,287
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	44,182	46,398
Business Transformation Services [Member] | Reportable Geographical Components [Member] | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,497	5,753
Business Transformation Services [Member] | Reportable Geographical Components [Member] | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenue	72	112
Business Transformation Services [Member] | Geography Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ (2,150)	$ (1,359)