GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Changes in Goodwill by Reportable Segment (Details) $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($)
Goodwill
Goodwill, net at December 31, 2018	$ 239.3
Measurement period adjustments for prior year business combinations	0.2
Goodwill, net at September 30, 2019	239.5
Ready-Mixed Concrete Segment
Goodwill
Goodwill, net at December 31, 2018	147.7
Measurement period adjustments for prior year business combinations	0.2
Goodwill, net at September 30, 2019	147.9
Aggregate Products Segment
Goodwill
Goodwill, net at December 31, 2018	86.2
Measurement period adjustments for prior year business combinations	0.0
Goodwill, net at September 30, 2019	86.2
Other Non-Reportable Segments
Goodwill
Goodwill, net at December 31, 2018	5.4
Measurement period adjustments for prior year business combinations	0.0
Goodwill, net at September 30, 2019	5.4
2018 Acquisitions
Goodwill
Adjustments for additional property, plant, and equipment	0.2
2018 Acquisitions \| Ready-Mixed Concrete Segment
Goodwill
Goodwill, net at December 31, 2018	$ 12.8

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to property, plant, and equipment acquired in connection with a business combination for which the initial accounting was incomplete.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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