SEGMENT REPORTING (Geographical Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 858,204	$ 843,181	$ 849,140	$ 749,778	$ 747,403	$ 755,846	$ 752,788	$ 688,941	$ 3,300,303	$ 2,944,978	$ 2,755,226
Percent of revenues									100.00%	100.00%	100.00%
Property, plant and equipment, net	$ 1,561,978				$ 1,587,365				$ 1,561,978	$ 1,587,365
Percent of property, plant and equipment, net	100.00%				100.00%				100.00%	100.00%
Permits and other intangibles, net	$ 441,875				$ 469,128				$ 441,875	$ 469,128
Percent of permits and other intangibles, net	100.00%				100.00%				100.00%	100.00%
Assets	$ 3,738,321				$ 3,706,570				$ 3,738,321	$ 3,706,570
United States
Segment Reporting Information [Line Items]
Revenues									2,796,145
Property, plant and equipment, net	$ 1,233,949				$ 1,175,437				$ 1,233,949	$ 1,175,437
Percent of property, plant and equipment, net	79.00%				74.00%				79.00%	74.00%
Permits and other intangibles, net	$ 393,045				$ 408,654				$ 393,045	$ 408,654
Percent of permits and other intangibles, net	88.90%				87.10%				88.90%	87.10%
Assets	$ 3,090,311				$ 2,985,394				$ 3,090,311	$ 2,985,394
Canada
Segment Reporting Information [Line Items]
Revenues									504,158
Property, plant and equipment, net	$ 328,029				$ 411,928				$ 328,029	$ 411,928
Percent of property, plant and equipment, net	21.00%				26.00%				21.00%	26.00%
Permits and other intangibles, net	$ 48,830				$ 60,474				$ 48,830	$ 60,474
Percent of permits and other intangibles, net	11.10%				12.90%				11.10%	12.90%
Assets	$ 648,010				$ 721,176				$ 648,010	$ 721,176
Direct revenues
Segment Reporting Information [Line Items]
Revenues									3,300,303	2,944,978	$ 2,755,226
Direct revenues | United States
Segment Reporting Information [Line Items]
Revenues									$ 2,721,814	$ 2,392,000	$ 2,213,355
Percent of revenues									82.50%	81.20%	80.30%
Direct revenues | Canada
Segment Reporting Information [Line Items]
Revenues									$ 578,489	$ 552,978	$ 541,871
Percent of revenues									17.50%	18.80%	19.70%