SEGMENT INFORMATION - Revenue by Product (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total revenue	$ 334.4	$ 333.1
Ready-mixed concrete
Segment Reporting Information [Line Items]
Total revenue	292.2	290.4
Aggregate products
Segment Reporting Information [Line Items]
Total revenue	31.1	31.8
Aggregates distribution
Segment Reporting Information [Line Items]
Total revenue	3.7	5.3
Building materials
Segment Reporting Information [Line Items]
Total revenue	6.3	4.6
Other
Segment Reporting Information [Line Items]
Total revenue	$ 1.1	$ 1.0