Revenue Recognition (Tables)

6 Months Ended

Jun. 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 reporting structure change described in Note 1.

	Three Months Ended
	June 30, 2020
	Products and Services		Freight		Total
	(Dollars in Millions)
Mid-America Group	$	362.9	$	29.4	$	392.3
Southeast Group		136.8		5.4		142.2
West Group		640.9		41.6		682.5
Total Building Materials Business		1,140.6		76.4		1,217.0
Magnesia Specialties		48.9		4.7		53.6
Total	$	1,189.5	$	81.1	$	1,270.6
	Three Months Ended
	June 30, 2019
	Products and Services		Freight		Total
	(Dollars in Millions)
Mid-America Group	$	381.9	$	32.6	$	414.5
Southeast Group		132.0		5.0		137.0
West Group		611.8		39.9		651.7
Total Building Materials Business		1,125.7		77.5		1,203.2
Magnesia Specialties		70.4		5.9		76.3
Total	$	1,196.1	$	83.4	$	1,279.5

	Six Months Ended
	June 30, 2020
	Products and Services		Freight		Total
	(Dollars in Millions)
Mid-America Group	$	603.9	$	49.2	$	653.1
Southeast Group		253.7		9.7		263.4
West Group		1,114.1		79.0		1,193.1
Total Building Materials Business		1,971.7		137.9		2,109.6
Magnesia Specialties		108.8		10.5		119.3
Total	$	2,080.5	$	148.4	$	2,228.9
	Six Months Ended
	June 30, 2019
	Products and Services		Freight		Total
	(Dollars in Millions)
Mid-America Group	$	611.5	$	51.1	$	662.6
Southeast Group		247.4		8.9		256.3
West Group		1,076.0		73.2		1,149.2
Total Building Materials Business		1,934.9		133.2		2,068.1
Magnesia Specialties		139.5		10.8		150.3
Total	$	2,074.4	$	144.0	$	2,218.4

Summary of Information About the Company's Contract Balances

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

(Dollars in Millions)	June 30, 2020		December 31, 2019
Costs in excess of billings	$	7.2	$	2.8
Billings in excess of costs	$	9.9	$	7.8