SEGMENT INFORMATION - Revenue by Product (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 327.4	$ 322.7	$ 613.1	$ 657.1
Ready-mixed concrete
Segment Reporting Information [Line Items]
Total revenue	274.3	272.4	515.8	564.6
Aggregate products
Segment Reporting Information [Line Items]
Total revenue	36.4	38.2	68.4	69.3
Other
Segment Reporting Information [Line Items]
Total revenue	$ 16.7	$ 12.1	$ 28.9	$ 23.2