BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Materials and supplies	$ 29,952	$ 30,843
Goodwill	664,118	$ 653,176
Acquisitions [Member]
Business Acquisition [Line Items]
Accounts receivable, net	504
Materials and supplies	128
Equipment and property	1,613
Goodwill	11,732
Customer contracts	17,994
Other intangible assets	291
Current liabilities	(142)
Other assets and liabilities, net	163
Total consideration paid	32,283
Less: Contingent consideration liability	(3,898)
Total cash purchase price	$ 28,385