BUSINESS COMBINATIONS (2015 Acquisitions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 453,105	$ 465,154	$ 452,669
Thermo Fluids Inc.
Business Acquisition [Line Items]
Accounts receivable	7,301
Accounts Receivables, measurement period adjustment	(284)
Inventories and supplies	1,791
Inventories and supplies, measurement period adjustment	0
Prepaid expenses and other current assets	665
Prepaid expenses and other current assets, measurement period adjustment	0
Property, plant and equipment	27,641
Property, plant and equipment, measurement period adjustment	(1,221)
Permits and other intangibles	18,100
Permits and other intangibles, measurement period adjustment	0
Current liabilities	(5,884)
Current liabilities, measurement period adjustment	(39)
Closure and post-closure liabilities, less current portion	(2,333)
Closure and post-closure liabilities, less current portion, measurement period adjustment	(657)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(9,174)
Deferred taxes, unrecognized tax benefits and other long-term liabilities, measurement period adjustments	856
Total identifiable net assets	38,107
Total identifiable net assets, measurement period adjustment	(1,345)
Goodwill	41,229
Goodwill, measurement period adjustment	2,095
Total purchase price, net of cash acquired	79,336
Total purchase price, net of cash acquired, measurement period adjustment	750
At Acquisition Dates | Thermo Fluids Inc.
Business Acquisition [Line Items]
Accounts receivable	7,585
Inventories and supplies	1,791
Prepaid expenses and other current assets	665
Property, plant and equipment	28,862
Permits and other intangibles	18,100
Current liabilities	(5,845)
Closure and post-closure liabilities, less current portion	(1,676)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(10,030)
Total identifiable net assets	39,452
Goodwill	39,134
Total purchase price, net of cash acquired	$ 78,586