Revenue Recognition (Tables)

6 Months Ended

Jun. 30, 2018

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:

	Three-Months Ended
	June 30, 2018
(Dollars in Thousands)	Products and Services		Freight		Total
Mid-America Group	$	325,578	$	25,014	$	350,592
Southeast Group		109,082		3,881		112,963
West Group		625,960		39,926		665,886
Total Building Materials Business		1,060,620		68,821		1,129,441
Magnesia Specialties		68,157		4,805		72,962
Total	$	1,128,777	$	73,626	$	1,202,403
	Three-Months Ended
	June 30, 2017
(Dollars in Thousands)	Products and Services		Freight		Total
Mid-America Group	$	269,914	$	20,984	$	290,898
Southeast Group		88,538		3,810		92,348
West Group		572,663		37,586		610,249
Total Building Materials Business		931,115		62,380		993,495
Magnesia Specialties		65,728		4,301		70,029
Total	$	996,843	$	66,681	$	1,063,524

2. Revenue Recognition (continued)

	Six-Months Ended
	June 30, 2018
(Dollars in Thousands)	Products and Services		Freight		Total
Mid-America Group	$	493,468	$	35,905	$	529,373
Southeast Group		186,646		6,556		193,202
West Group		1,068,943		70,665		1,139,608
Total Building Materials Business		1,749,057		113,126		1,862,183
Magnesia Specialties		133,025		9,199		142,224
Total	$	1,882,082	$	122,325	$	2,004,407
	Six-Months Ended
	June 30, 2017
(Dollars in Thousands)	Products and Services		Freight		Total
Mid-America Group	$	447,321	$	32,597	$	479,918
Southeast Group		175,264		7,366		182,630
West Group		1,036,545		69,685		1,106,230
Total Building Materials Business		1,659,130		109,648		1,768,778
Magnesia Specialties		130,029		8,576		138,605
Total	$	1,789,159	$	118,224	$	1,907,383

Summary of Information About the Company's Contract Balances

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

(Dollars in Thousands)	June 30, 2018		December 31, 2017		June 30, 2017
Costs in excess of billings	$	6,581	$	1,310	$	10,990
Billings in excess of costs	$	7,843	$	7,204	$	5,194