GOODWILL AND INTANGIBLE ASSETS, NET - Schedule of Changes in Goodwill by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill
Goodwill beginning balance	$ 239.3	$ 204.7
2018 acquisitions(1)		13.4
Measurement period adjustments for prior year business combinations	0.2	21.2
Goodwill ending balance	239.5	239.3	$ 204.7
Ready-Mixed Concrete Segment
Goodwill
Goodwill beginning balance	149.8	136.7
2018 acquisitions(1)		13.4
Measurement period adjustments for prior year business combinations	0.2	(0.3)
Goodwill ending balance	150.0	149.8	136.7
Purchase accounting adjustment to definite-lived and indefinite-lived intangible assets		0.8	1.3
Aggregate Products Segment
Goodwill
Goodwill beginning balance	86.2	56.1
2018 acquisitions(1)		0.0
Measurement period adjustments for prior year business combinations	0.0	30.1
Goodwill ending balance	86.2	86.2	56.1
Other Non-Reportable Segments
Goodwill
Goodwill beginning balance	3.3	11.9
2018 acquisitions(1)		0.0
Measurement period adjustments for prior year business combinations	0.0	(8.6)
Goodwill ending balance	3.3	3.3	$ 11.9
Acquisitions 2017
Goodwill
Purchase accounting adjustment to definite-lived and indefinite-lived intangible assets		0.3
Additional long-term obligations recorded for 2017 acquisitions		21.0
Deferred taxes attributable to fair value adjustments		18.6
Assumed liabilities		2.8
Working capital		0.4
Purchase accounting adjustment to property, plant and equipment		2.7
Goodwill, reclassifications		8.6
2018 Acquisitions
Goodwill
Goodwill beginning balance	13.6
Goodwill ending balance		13.6
Purchase accounting adjustment to definite-lived and indefinite-lived intangible assets	0.5	0.2
Purchase accounting adjustment to property, plant and equipment	(0.2)
2018 Acquisitions | Ready-Mixed Concrete Segment
Goodwill
Goodwill beginning balance	$ 12.8
Goodwill ending balance		$ 12.8