ACQUISITIONS AND DIVESTITURES (Narrative) (Details) - USD ($)	3 Months Ended				6 Months Ended			12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Significant Acquisitions and Disposals [Line Items]
Cash consideration						$ 0	$ 5,668,000
Gain on sale of property, plant & equipment and businesses	$ 211,000			$ (258,000)		117,376,000	741,000
Assets held for sale	$ 0		$ 0	$ 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
Forecast [Member] | U.S. Concrete, Inc. [Member]
Significant Acquisitions and Disposals [Line Items]
Total consideration					$ 1,294,000,000
Business acquisition, price per share					$ 74.00