ACQUISITIONS AND DIVESTITURES (Narrative) (Details) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Significant Acquisitions and Disposals [Line Items]
Cash consideration				$ 43,223	$ 44,151	$ 221,419
Goodwill	[1]			5,051	1,665
Gain on sale of property, plant & equipment and businesses		$ 4,064		3,997	23,752	14,944
Assets held for sale				0	0	0
Acquisitions 2020 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration				73,416
Cash consideration				43,223
Consideration payable amount				30,193
Amortizable intangible assets recognized				$ 65,545
Intangible assets amortization period, tax purposes				15 years
Goodwill				$ 5,051
Intangible assets, not deductible for income tax purposes				$ 25,712
Acquisitions 2019 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration					45,273
Amortizable intangible assets recognized					25,443
Intangible assets amortization period, tax purposes				15 years
Acquisitions 2018 [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration						219,863
Cash consideration						215,363
Consideration payable amount						4,500
Amortizable intangible assets recognized						44,163
Intangible assets amortization period, tax purposes				15 years
Goodwill						43,990
Intangible assets, deductible for income tax purposes						7,385
Goodwill, deductible for income tax purposes						4,863
Deferred income taxes, net				$ 31,721
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
Georgia [Member]
Significant Acquisitions and Disposals [Line Items]
Gain on sale of property, plant & equipment and businesses			$ 2,929
Aggregates [Member]
Significant Acquisitions and Disposals [Line Items]
Goodwill	[1]			$ 5,051	$ 1,665
Aggregates [Member] | Georgia [Member]
Significant Acquisitions and Disposals [Line Items]
Number of facilities divested | item					2
Contractual Rights In Place - Straight-Line Method [Member] | Acquisitions 2020 [Member]
Significant Acquisitions and Disposals [Line Items]
Amortizable intangible assets recognized				$ 25,712
Estimated weighted-average amortization period of intangible assets				20 years
Contractual Rights In Place - Straight-Line Method [Member] | Acquisitions 2019 [Member]
Significant Acquisitions and Disposals [Line Items]
Estimated weighted-average amortization period of intangible assets				19 years 6 months
Contractual Rights In Place - Straight-Line Method [Member] | Acquisitions 2018 [Member]
Significant Acquisitions and Disposals [Line Items]
Amortizable intangible assets recognized						43,072
Estimated weighted-average amortization period of intangible assets				19 years 10 months 24 days
Contractual Rights In Place - Units Of Sales [Member] | Acquisitions 2018 [Member]
Significant Acquisitions and Disposals [Line Items]
Amortizable intangible assets recognized						$ 1,080
Estimated weighted-average amortization period of intangible assets				30 years

[1] See Note 19 for a summary of recent acquisitions.