BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 260,154	$ 249,939
Acquisition [Member]
Business Acquisition [Line Items]
Accounts receivable	3,185
Materials and supplies	352
Equipment and property	4,039
Goodwill	8,613
Customer contracts	40,861
Other intangible assets	1,065
Current liabilities	(6,836)
Other assets and liabilities, net	(2,836)
Total consideration paid	48,443
Less: Contingent consideration liability	(7,619)
Total cash purchase price	$ 40,824