ACQUISITIONS AND DIVESTITURES (Narrative) (Details)		3 Months Ended			9 Months Ended		12 Months Ended
		Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Significant Acquisitions and Disposals [Line Items]
Cash consideration					$ 5,668,000	$ (1,122,000)
Number of facilities divested | item					2
Goodwill	[1]				$ 5,051,000
Gain on sale of property, plant & equipment and businesses		$ 1,576,000	$ 234,000		2,317,000	10,982,000
Assets held for sale		$ 0	$ 0		0	$ 0	$ 0
Acquisitions 2020 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration					35,862,000
Amortizable intangible assets recognized					$ 39,779,000
Estimated weighted-average amortization period of intangible assets					20 years
Goodwill					$ 5,051,000
Acquisitions 2019 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration							45,273,000
Amortizable intangible assets recognized							$ 25,443,000
Estimated weighted-average amortization period of intangible assets					19 years 6 months
Intangible assets amortization period, tax purposes					15 years
New Mexico [Member]
Significant Acquisitions and Disposals [Line Items]
Supply agreement period		20 years
Georgia [Member]
Significant Acquisitions and Disposals [Line Items]
Gain on sale of property, plant & equipment and businesses				$ 4,064,000

[1] See Note 16 for a summary of recent acquisitions.