SEGMENT REPORTING (Geographical Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,525,298	$ 1,588,151
Percent of property, plant and equipment, net	100.00%	100.00%
Permits and other intangibles, net	$ 386,620	$ 419,066
Percent of permits and other intangibles, net	100.00%	100.00%
Assets	$ 4,131,520	$ 4,108,904
United States
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,246,758	$ 1,273,205
Percent of property, plant and equipment, net	81.70%	80.20%
Permits and other intangibles, net	$ 342,787	$ 372,609
Percent of permits and other intangibles, net	88.70%	88.90%
Assets	$ 3,447,811	$ 3,413,254
Canada
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 278,540	$ 314,946
Percent of property, plant and equipment, net	18.30%	19.80%
Permits and other intangibles, net	$ 43,833	$ 46,457
Percent of permits and other intangibles, net	11.30%	11.10%
Assets	$ 683,709	$ 695,650