Revenue Recognition (Tables)

9 Months Ended

Sep. 30, 2020

Revenue From Contract With Customer [Abstract]

Schedule of Company's Total Revenues by Category for each Reportable Segment

The following table presents the Company’s total revenues by category for each reportable segment. Prior-year segment information has been reclassified to conform to the reportable segment changes described in Note 1.

	Three Months Ended
	September 30, 2020
	Products and Services		Freight		Total
	(Dollars in Millions)
East Group	$	514.1	$	35.2	$	549.3
West Group		671.4		39.8		711.2
Total Building Materials Business		1,185.5		75.0		1,260.5
Magnesia Specialties		55.2		5.7		60.9
Total	$	1,240.7	$	80.7	$	1,321.4
	Three Months Ended
	September 30, 2019
	Products and Services		Freight		Total
	(Dollars in Millions)
East Group	$	539.8	$	42.2	$	582.0
West Group		724.1		49.3		773.4
Total Building Materials Business		1,263.9		91.5		1,355.4
Magnesia Specialties		59.3		5.5		64.8
Total	$	1,323.2	$	97.0	$	1,420.2

	Nine Months Ended
	September 30, 2020
	Products and Services		Freight		Total
	(Dollars in Millions)
East Group	$	1,371.8	$	94.1	$	1,465.9
West Group		1,785.4		118.8		1,904.2
Total Building Materials Business		3,157.2		212.9		3,370.1
Magnesia Specialties		164.0		16.2		180.2
Total	$	3,321.2	$	229.1	$	3,550.3
	Nine Months Ended
	September 30, 2019
	Products and Services		Freight		Total
	(Dollars in Millions)
East Group	$	1,398.6	$	102.2	$	1,500.8
West Group		1,800.1		122.6		1,922.7
Total Building Materials Business		3,198.7		224.8		3,423.5
Magnesia Specialties		198.9		16.3		215.2
Total	$	3,397.6	$	241.1	$	3,638.7

Summary of Information About the Company's Contract Balances

The following table presents information about the Company’s contract balances:

(Dollars in Millions)	September 30, 2020		December 31, 2019
Costs in excess of billings	$	8.1	$	2.8
Billings in excess of costs	$	13.0	$	7.8