BUSINESS COMBINATIONS (2016 Acquisitions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 465,154	$ 478,523	$ 453,105
2016 Acquisitions
Business Acquisition [Line Items]
Accounts receivable	16,242
Accounts receivables, measurement period adjustment	475
Inventories and supplies	12,688
Inventories and supplies, measurement period adjustment	173
Prepaid expenses and other current assets	752
Prepaid expenses and other current assets, measurement period adjustment	(25)
Property, plant and equipment	143,916
Property, plant and equipment, measurement period adjustment	891
Permits and other intangibles	28,856
Permits and other intangibles, measurement period adjustment	0
Current liabilities	(19,905)
Current liabilities, measurement period adjustment	353
Closure and post-closure liabilities, less current portion	(3,004)
Closure and post-closure liabilities, less current portion, measurement period adjustment	(596)
Remedial liabilities, less current portion	(2,545)
Remedial liabilities, less current portion, measurement period adjustment	(504)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(20,219)
Deferred taxes, unrecognized tax benefits and other long-term liabilities, measurement period adjustments	(3,200)
Total identifiable net assets	156,781
Total identifiable net assets, measurement period adjustment	(2,433)
Goodwill	47,977
Goodwill, measurement period adjustment	2,186
Total purchase price, net of cash acquired	204,758
Total purchase price, net of cash acquired, measurement period adjustment	(247)
At Acquisition Dates As Reported December 31, 2016 | 2016 Acquisitions
Business Acquisition [Line Items]
Accounts receivable	15,767
Inventories and supplies	12,515
Prepaid expenses and other current assets	777
Property, plant and equipment	143,025
Permits and other intangibles	28,856
Current liabilities	(20,258)
Closure and post-closure liabilities, less current portion	(2,408)
Remedial liabilities, less current portion	(2,041)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(17,019)
Total identifiable net assets	159,214
Goodwill	45,791
Total purchase price, net of cash acquired	$ 205,005