SEGMENT INFORMATION - Reconciliation of Total Reportable Segment Adjusted EBITDA to Income (Loss) From Continuing Operations (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) reporting_segment	Jun. 30, 2020 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | reporting_segment			2
Revenue by Segment:
Revenue	$ 327.4	$ 322.7	$ 613.1	$ 657.1
Reconciliation of Total Reportable Segment Adjusted EBITDA to Net Income (Loss):
Total reportable segment Adjusted EBITDA	51.0	59.7	88.4	102.7
Other products and eliminations from operations	0.7	0.3	0.4	0.4
Corporate overhead	(32.6)	(16.3)	(46.3)	(31.9)
Depreciation, depletion and amortization for reportable segments	(24.2)	(23.7)	(47.1)	(45.5)
Interest expense, net	(10.3)	(11.4)	(20.7)	(22.8)
Loss on extinguishment of debt	(5.5)	0.0	(5.5)	0.0
Gain on sale of business	0.0	0.0	0.7	0.0
Realignment initiative costs	0.0	(0.8)	(0.4)	(0.8)
Change in value of contingent consideration for reportable segments	0.0	5.8	0.1	5.5
Purchase accounting adjustments for inventory	(0.5)	(2.6)	(0.6)	(4.2)
Corporate, other products and eliminations other income (loss), net	0.2	(0.2)	0.3	(0.3)
Income (loss) before income taxes	(21.2)	10.8	(30.7)	3.1
Income tax benefit (expense)	0.7	(4.3)	5.4	0.6
Net income (loss)	(20.5)	6.5	(25.3)	3.7
Ready-mixed concrete
Revenue by Segment:
Revenue	274.3	272.4	515.8	564.6
Reconciliation of Total Reportable Segment Adjusted EBITDA to Net Income (Loss):
Total reportable segment Adjusted EBITDA	30.9	38.1	55.8	69.8
Aggregate products
Revenue by Segment:
Revenue	25.2	26.1	47.8	47.2
Reconciliation of Total Reportable Segment Adjusted EBITDA to Net Income (Loss):
Total reportable segment Adjusted EBITDA	20.1	21.6	32.6	32.9
Aggregate products | Cargo and Freight
Revenue by Segment:
Revenue	11.2	12.1	20.6	22.1
Operating segment
Revenue by Segment:
Revenue	327.5	326.9	613.5	662.7
Operating segment | Aggregate products
Revenue by Segment:
Revenue	53.2	54.5	97.7	98.1
Intersegment sales | Aggregate products
Revenue by Segment:
Revenue	16.8	16.3	29.3	28.8
Other products and corporate
Revenue by Segment:
Revenue	$ (0.1)	$ (4.2)	$ (0.4)	$ (5.6)