ACQUISITIONS AND DIVESTITURES (Narrative) (Details) - USD ($)	3 Months Ended				12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020
Significant Acquisitions and Disposals [Line Items]
Gain on sale of property, plant & equipment and businesses	$ 117,165,000			$ 999,000
Assets held for sale	0	$ 0		$ 0	$ 0
Acquisitions 2020 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration					73,416,000
Cash consideration	43,223,000
Consideration payable amount	30,193,000
Amortizable intangible assets recognized					$ 65,545,000
Intangible assets amortization period, tax purposes					15 years
Goodwill					$ 5,051,000
Intangible assets, deductible for income tax purposes		$ 25,712,000			25,712,000
California [Member]
Significant Acquisitions and Disposals [Line Items]
Consideration transferred, net of assets divested	12,900,000
Gain on sale of property, plant & equipment and businesses	$ 114,695,000
New Mexico [Member]
Significant Acquisitions and Disposals [Line Items]
Supply agreement period			20 years
Virginia [Member]
Significant Acquisitions and Disposals [Line Items]
Supply agreement period		20 years
Amortizable Intangible Asset Straight-Line Method [Member] | Acquisitions 2020 [Member]
Significant Acquisitions and Disposals [Line Items]
Amortizable intangible assets recognized					$ 65,545,000
Estimated weighted-average amortization period of intangible assets					20 years