ACQUISITIONS - Furmanite (Additional Information) (Details) $ in Thousands		3 Months Ended	9 Months Ended
	Feb. 29, 2016 USD ($) shares	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill				$ 284,680	$ 355,786
Furmanite Corporation
Business Acquisition [Line Items]
Number of shares received for each share of common stock owned	0.215
Business acquisition, purchase price	$ 282,341
Number of common shares issued | shares	8,208,006
Acquired intangible assets	$ 88,958
Goodwill	89,646
Acquired receivables, gross contractual amount	88,000
Furmanite Corporation | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Total acquisition costs		$ 200	$ 6,800
Separately recognized transaction, acquisition-related compensation costs		$ 0	$ 4,700
Furmanite Corporation | Customer Relationships
Business Acquisition [Line Items]
Acquired intangible assets	$ 69,800
Acquired intangible asset useful life	12 years
Furmanite Corporation | Trade Names
Business Acquisition [Line Items]
Acquired intangible assets	$ 16,900
Acquired intangible asset useful life	12 years
Furmanite Corporation | Developed Technology
Business Acquisition [Line Items]
Acquired intangible assets	$ 2,300
Acquired intangible asset useful life	10 years
Continuing Operations | Furmanite Corporation
Business Acquisition [Line Items]
Acquired receivables, fair value	$ 65,900
Acquired receivables, estimated uncollectible	7,900
Discontinued Operations | Furmanite Corporation
Business Acquisition [Line Items]
Acquired intangible assets	1,600
Goodwill	3,300
Acquired receivables, fair value	13,600
Costs to sell, discontinued operations	$ 1,100