CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Total revenues	[1]	$ 4,382,869	$ 3,890,296	$ 3,592,667
Cost of revenues		3,281,924	2,896,783	2,603,782
Gross profit		1,100,945	993,513	988,885
Selling, administrative and general expenses		333,371	324,972	316,769
Gain on sale of property, plant & equipment and businesses		14,944	17,827	15,431
Other operating expense, net		(34,805)	(47,324)	(21,645)
Operating earnings		747,713	639,044	665,902
Other nonoperating income, net		13,000	13,357	14,624
Interest income		554	4,437	807
Interest expense		137,977	295,522	134,076
Earnings from continuing operations before income taxes		623,290	361,316	547,257
Income tax expense (benefit)
Current		40,516	354	94,254
Deferred		64,933	(232,429)	30,597
Total income tax expense (benefit)		105,449	(232,075)	124,851
Earnings from continuing operations		517,841	593,391	422,406
Earnings (loss) on discontinued operations, net of tax		(2,036)	7,794	(2,915)
Net earnings		515,805	601,185	419,491
Other comprehensive income (loss), net of tax
Deferred gain on interest rate derivative		2,496	0	0
Amortization of prior interest rate derivative loss		226	1,862	1,194
Adjustment for funded status of benefit plans		(207)	(14,106)	(20,583)
Amortization of actuarial loss and prior service cost for benefit plans		4,365	2,154	82
Other comprehensive income (loss)		6,880	(10,090)	(19,307)
Comprehensive income		$ 522,685	$ 591,095	$ 400,184
Basic earnings (loss) per share
Continuing operations		$ 3.91	$ 4.48	$ 3.17
Discontinued operations		(0.01)	0.06	(0.02)
Net earnings		3.90	4.54	3.15
Diluted earnings (loss) per share
Continuing operations		3.87	4.40	3.11
Discontinued operations		(0.02)	0.06	(0.02)
Net earnings		$ 3.85	$ 4.46	$ 3.09
Weighted-average common shares outstanding
Basic		132,393	132,513	133,205
Assuming dilution		133,926	134,878	135,790

[1] The geographic markets are defined by states/countries as follows:East market - Arkansas, Delaware, Illinois, Kentucky, Maryland, North Carolina, Pennsylvania, Tennessee, Virginia, and Washington D.C.Gulf Coast market - Alabama, Florida, Georgia, Louisiana, Mexico, Mississippi, Oklahoma, South Carolina, Texas and the BahamasWest market - Arizona, California and New Mexico