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Revenue - Disaggregated Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 174,556	$ 147,894	$ 505,968	$ 431,794
United States
Disaggregation of Revenue [Line Items]
Revenue	122,948	101,405	352,547	301,596
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	22,650	19,818	64,438	53,167
Europe
Disaggregation of Revenue [Line Items]
Revenue	26,620	25,054	83,094	71,578
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	2,338	1,617	5,889	5,453
Oil & Gas
Disaggregation of Revenue [Line Items]
Revenue	97,498	81,995	291,805	241,179
Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenue	16,715	14,652	49,825	54,860
Industrials
Disaggregation of Revenue [Line Items]
Revenue	17,589	17,912	49,438	50,720
Power Generation & Transmission
Disaggregation of Revenue [Line Items]
Revenue	14,687	11,497	37,044	28,646
Other Process Industries
Disaggregation of Revenue [Line Items]
Revenue	11,886	8,481	36,681	24,291
Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenue	10,411	8,777	27,733	23,229
Other
Disaggregation of Revenue [Line Items]
Revenue	5,770	4,580	13,442	8,869
Operating segments | Services
Disaggregation of Revenue [Line Items]
Revenue	144,976	119,721	414,251	349,271
Operating segments | Services | United States
Disaggregation of Revenue [Line Items]
Revenue	122,506	100,586	349,814	298,372
Operating segments | Services | Other Americas
Disaggregation of Revenue [Line Items]
Revenue	21,681	18,767	61,847	49,548
Operating segments | Services | Europe
Disaggregation of Revenue [Line Items]
Revenue	491	350	1,381	721
Operating segments | Services | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	298	18	1,209	630
Operating segments | Services | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenue	88,508	72,195	264,959	214,773
Operating segments | Services | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenue	12,717	10,904	37,319	39,804
Operating segments | Services | Industrials
Disaggregation of Revenue [Line Items]
Revenue	10,560	12,209	30,621	35,374
Operating segments | Services | Power Generation & Transmission
Disaggregation of Revenue [Line Items]
Revenue	11,412	9,053	27,019	21,800
Operating segments | Services | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenue	8,819	6,023	27,031	17,026
Operating segments | Services | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenue	7,136	5,309	15,479	12,820
Operating segments | Services | Other
Disaggregation of Revenue [Line Items]
Revenue	5,824	4,028	11,823	7,674
Operating segments | International
Disaggregation of Revenue [Line Items]
Revenue	29,100	26,477	88,699	76,887
Operating segments | International | United States
Disaggregation of Revenue [Line Items]
Revenue	221	193	670	507
Operating segments | International | Other Americas
Disaggregation of Revenue [Line Items]
Revenue	1,446	1,100	3,772	3,564
Operating segments | International | Europe
Disaggregation of Revenue [Line Items]
Revenue	26,378	24,790	82,356	71,056
Operating segments | International | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	1,055	394	1,901	1,760
Operating segments | International | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenue	8,620	9,749	26,208	26,192
Operating segments | International | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenue	3,897	3,676	12,341	14,686
Operating segments | International | Industrials
Disaggregation of Revenue [Line Items]
Revenue	6,693	5,261	17,736	13,997
Operating segments | International | Power Generation & Transmission
Disaggregation of Revenue [Line Items]
Revenue	2,615	2,054	7,776	4,958
Operating segments | International | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenue	3,035	2,373	9,574	7,103
Operating segments | International | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenue	2,467	2,245	9,477	6,726
Operating segments | International | Other
Disaggregation of Revenue [Line Items]
Revenue	1,773	1,119	5,587	3,225
Operating segments | Products
Disaggregation of Revenue [Line Items]
Revenue	3,308	3,932	9,499	10,746
Operating segments | Products | United States
Disaggregation of Revenue [Line Items]
Revenue	1,562	1,538	4,690	5,150
Operating segments | Products | Other Americas
Disaggregation of Revenue [Line Items]
Revenue	133	75	301	425
Operating segments | Products | Europe
Disaggregation of Revenue [Line Items]
Revenue	499	1,002	1,462	1,930
Operating segments | Products | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	1,114	1,317	3,046	3,241
Operating segments | Products | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenue	370	51	638	214
Operating segments | Products | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenue	101	72	165	370
Operating segments | Products | Industrials
Disaggregation of Revenue [Line Items]
Revenue	336	442	1,081	1,349
Operating segments | Products | Power Generation & Transmission
Disaggregation of Revenue [Line Items]
Revenue	660	390	2,249	1,888
Operating segments | Products | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenue	32	85	76	162
Operating segments | Products | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenue	808	1,223	2,777	3,683
Operating segments | Products | Other
Disaggregation of Revenue [Line Items]
Revenue	1,001	1,669	2,513	3,080
Corp/Elim
Disaggregation of Revenue [Line Items]
Revenue	(2,828)	(2,236)	(6,481)	(5,110)
Corp/Elim | United States
Disaggregation of Revenue [Line Items]
Revenue	(1,341)	(912)	(2,627)	(2,433)
Corp/Elim | Other Americas
Disaggregation of Revenue [Line Items]
Revenue	(610)	(124)	(1,482)	(370)
Corp/Elim | Europe
Disaggregation of Revenue [Line Items]
Revenue	(748)	(1,088)	(2,105)	(2,129)
Corp/Elim | Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	(129)	(112)	(267)	(178)
Corp/Elim | Oil & Gas
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Aerospace & Defense
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Industrials
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Power Generation & Transmission
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Other Process Industries
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Infrastructure, Research & Engineering
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Corp/Elim | Other
Disaggregation of Revenue [Line Items]
Revenue	$ (2,828)	$ (2,236)	$ (6,481)	$ (5,110)

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