Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues	$ 309,799	$ 290,856	$ 343,889	$ 302,385	$ 316,334	$ 285,067	$ 312,256	$ 286,554	$ 1,246,929	$ 1,200,211	$ 1,196,696
United States and Canada
Disaggregation of Revenue [Line Items]
Revenues									1,048,282
Other Countries
Disaggregation of Revenue [Line Items]
Revenues									198,647
Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues									144,314
Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues									551,121
Heat Treating
Disaggregation of Revenue [Line Items]
Revenues									83,593
Non-Destructive Evaluation
Disaggregation of Revenue [Line Items]
Revenues									447,080
Other Services
Disaggregation of Revenue [Line Items]
Revenues									20,821
IHT
Disaggregation of Revenue [Line Items]
Revenues									617,378
IHT | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues									602,615
IHT | Other Countries
Disaggregation of Revenue [Line Items]
Revenues									14,763
IHT | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues									46,726
IHT | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues									27,420
IHT | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues									80,840
IHT | Non-Destructive Evaluation
Disaggregation of Revenue [Line Items]
Revenues									447,080
IHT | Other Services
Disaggregation of Revenue [Line Items]
Revenues									15,312
MS
Disaggregation of Revenue [Line Items]
Revenues									532,365
MS | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues									383,405
MS | Other Countries
Disaggregation of Revenue [Line Items]
Revenues									148,960
MS | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues									402
MS | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues									523,701
MS | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues									2,753
MS | Non-Destructive Evaluation
Disaggregation of Revenue [Line Items]
Revenues									0
MS | Other Services
Disaggregation of Revenue [Line Items]
Revenues									5,509
Quest Integrity
Disaggregation of Revenue [Line Items]
Revenues									97,186
Quest Integrity | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues									62,262
Quest Integrity | Other Countries
Disaggregation of Revenue [Line Items]
Revenues									34,924
Quest Integrity | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues									97,186
Quest Integrity | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues									0
Quest Integrity | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues									0
Quest Integrity | Non-Destructive Evaluation
Disaggregation of Revenue [Line Items]
Revenues									0
Quest Integrity | Other Services
Disaggregation of Revenue [Line Items]
Revenues									$ 0