RESTRUCTURING AND OTHER RELATED CHARGES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	$ 2,047	$ 2,637	$ 4,458	$ 1,661
OneTeam Program
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	2,047		4,458
OneTeam Program | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net			4,458
Exit activities, costs incurred to date	4,500		4,500
OneTeam Program | Employee Severance | IHT
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	468		1,436
OneTeam Program | Employee Severance | MS
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	408		739
OneTeam Program | Employee Severance | Quest Integrity
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	7		40
OneTeam Program | Employee Severance | Corporate and shared support services
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	1,164		2,243
2017 Cost Savings Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	0	2,632	0	2,869
2017 Cost Savings Initiative | Employee Severance
Restructuring Cost and Reserve [Line Items]
Exit activities, costs incurred to date	3,900		3,900
2017 Cost Savings Initiative | Employee Severance | IHT
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net		862		862
2017 Cost Savings Initiative | Employee Severance | MS
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net		1,219		1,219
2017 Cost Savings Initiative | Employee Severance | Quest Integrity
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net		424		424
2017 Cost Savings Initiative | Employee Severance | Corporate and shared support services
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net		127		364
Furmanite Netherlands and Belgium Exit
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	0	5	0	(1,208)
Gain on disposal				1,100	$ 1,100
Furmanite Netherlands and Belgium Exit | MS
Restructuring Cost and Reserve [Line Items]
Gain on disposal	0	0	0	(1,056)
Furmanite Netherlands and Belgium Exit | Employee Severance
Restructuring Cost and Reserve [Line Items]
Exit activities, costs incurred to date	4,700		4,700
Furmanite Netherlands and Belgium Exit | Employee Severance | MS
Restructuring Cost and Reserve [Line Items]
Restructuring and other related charges, net	0	$ 5	0	$ (152)
Furmanite Netherlands and Belgium Exit | Impairment Loss On Property, Plant And Equipment
Restructuring Cost and Reserve [Line Items]
Exit activities, costs incurred to date	$ 700		$ 700