SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND PRACTICES - Additional Information (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) country shares	Jun. 30, 2015 USD ($) shares	Jun. 30, 2016 USD ($) location country segment classification customer shares	Jun. 30, 2015 USD ($) shares	Dec. 31, 2015 USD ($)	Dec. 01, 2015 USD ($)	Jul. 07, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounting Policies [Abstract]
Number of operating segments | segment			3
Number of service classifications | classification			3
Number of locations in which company operates (more than) | location			220
Number of countries in which the company operates | country	22		22
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 65,440,000	$ 31,877,000	$ 65,440,000	$ 31,877,000	$ 44,825,000			$ 44,426,000
Restricted cash	0		$ 0		5,000,000
Goodwill impairment					0
Discounted cash flow, forecast period			4 years
Market capitalization in excess of consolidated net assets						$ 482,000,000
Market capitalization in excess of consolidated net assets, percentage						141.00%
Goodwill	361,961,000		$ 361,961,000		256,654,000
Income tax expense as a percentage of pre-tax income from continuing operations			3.10%	35.70%
Measurement-period adjustment, deferred tax liabilities, increase	47,900,000
Workers compensation our self-insured retention			$ 1,000,000.0
Automobile liability self-insured retention			500,000
General liability claims we have an effective self-insured retention			3,000,000.0
Medical claims, our self-insured retention			175,000
Environmental liability claims, our self-insured retention			1,000,000
Amount of earned but unbilled revenue included in accounts receivable	$ 73,300,000		$ 73,300,000		47,100,000
Options to purchase shares of common stock excluded from the computation of diluted earnings per share | shares	300,000	0	400,000	0
Sales Revenue, Net | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Number of customers accounted for more than specified percentage of consolidated revenues | customer			0
Qualspec Group
Significant Accounting Policies [Line Items]
Restricted cash					5,000,000
Goodwill							$ 148,482,000
Europe and Canada
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 14,900,000		$ 14,900,000		$ 17,500,000