Revenue - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 159,465	$ 176,787
United States
Disaggregation of Revenue [Line Items]
Revenues	110,583	114,100
Other Americas
Disaggregation of Revenue [Line Items]
Revenues	20,365	28,947
Europe
Disaggregation of Revenue [Line Items]
Revenues	26,304	31,626
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	2,213	2,114
Oil & Gas
Disaggregation of Revenue [Line Items]
Revenues	92,498	101,385
Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenues	22,214	24,755
Industrials
Disaggregation of Revenue [Line Items]
Revenues	18,274	21,630
Power generation & Transmission
Disaggregation of Revenue [Line Items]
Revenues	7,646	9,064
Other Process Industries
Disaggregation of Revenue [Line Items]
Revenues	8,127	8,566
Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenues	7,538	6,170
Other
Disaggregation of Revenue [Line Items]
Revenues	3,168	5,217
Operating segments | Services
Disaggregation of Revenue [Line Items]
Revenues	128,873	140,298
Operating segments | Services | United States
Disaggregation of Revenue [Line Items]
Revenues	109,581	113,136
Operating segments | Services | Other Americas
Disaggregation of Revenue [Line Items]
Revenues	18,735	26,708
Operating segments | Services | Europe
Disaggregation of Revenue [Line Items]
Revenues	108	428
Operating segments | Services | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	449	26
Operating segments | Services | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenues	83,299	91,666
Operating segments | Services | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenues	14,652	12,794
Operating segments | Services | Industrials
Disaggregation of Revenue [Line Items]
Revenues	12,867	16,123
Operating segments | Services | Power generation & Transmission
Disaggregation of Revenue [Line Items]
Revenues	5,095	6,262
Operating segments | Services | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenues	6,004	6,319
Operating segments | Services | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenues	4,517	2,590
Operating segments | Services | Other
Disaggregation of Revenue [Line Items]
Revenues	2,439	4,544
Operating segments | International
Disaggregation of Revenue [Line Items]
Revenues	29,067	35,162
Operating segments | International | United States
Disaggregation of Revenue [Line Items]
Revenues	154	276
Operating segments | International | Other Americas
Disaggregation of Revenue [Line Items]
Revenues	1,505	2,229
Operating segments | International | Europe
Disaggregation of Revenue [Line Items]
Revenues	26,235	31,540
Operating segments | International | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	1,173	1,117
Operating segments | International | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenues	9,104	9,704
Operating segments | International | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenues	7,415	11,654
Operating segments | International | Industrials
Disaggregation of Revenue [Line Items]
Revenues	4,919	5,075
Operating segments | International | Power generation & Transmission
Disaggregation of Revenue [Line Items]
Revenues	1,697	1,422
Operating segments | International | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenues	2,120	2,242
Operating segments | International | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenues	2,461	2,733
Operating segments | International | Other
Disaggregation of Revenue [Line Items]
Revenues	1,351	2,332
Operating segments | Products
Disaggregation of Revenue [Line Items]
Revenues	2,812	3,432
Operating segments | Products | United States
Disaggregation of Revenue [Line Items]
Revenues	1,559	1,970
Operating segments | Products | Other Americas
Disaggregation of Revenue [Line Items]
Revenues	278	66
Operating segments | Products | Europe
Disaggregation of Revenue [Line Items]
Revenues	340	421
Operating segments | Products | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	635	975
Operating segments | Products | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenues	95	15
Operating segments | Products | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenues	147	307
Operating segments | Products | Industrials
Disaggregation of Revenue [Line Items]
Revenues	488	432
Operating segments | Products | Power generation & Transmission
Disaggregation of Revenue [Line Items]
Revenues	854	1,380
Operating segments | Products | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenues	3	5
Operating segments | Products | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenues	560	847
Operating segments | Products | Other
Disaggregation of Revenue [Line Items]
Revenues	665	446
Corp/Elim
Disaggregation of Revenue [Line Items]
Revenues	(1,287)	(2,105)
Corp/Elim | United States
Disaggregation of Revenue [Line Items]
Revenues	(711)	(1,282)
Corp/Elim | Other Americas
Disaggregation of Revenue [Line Items]
Revenues	(153)	(56)
Corp/Elim | Europe
Disaggregation of Revenue [Line Items]
Revenues	(379)	(763)
Corp/Elim | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	(44)	(4)
Corp/Elim | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Industrials
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Power generation & Transmission
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corp/Elim | Other
Disaggregation of Revenue [Line Items]
Revenues	$ (1,287)	$ (2,105)