CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Total revenues	$ 3,592,667	$ 3,422,181	$ 2,994,169
Cost of revenues	2,591,850	2,564,648	2,406,587
Gross profit	1,000,817	857,533	587,582
Selling, administrative and general expenses	314,986	286,844	272,288
Gain on sale of property, plant & equipment and businesses	15,431	9,927	244,222
Business interruption claims recovery	11,652	0	0
Impairment of long-lived assets	(10,506)	(5,190)	(3,095)
Other operating expense, net	(22,826)	(25,648)	(18,283)
Operating earnings	679,582	549,778	538,138
Other nonoperating income (expense), net	944	(1,678)	3,107
Interest income	807	345	960
Interest expense	134,076	220,588	243,367
Earnings from continuing operations before income taxes	547,257	327,857	298,838
Income tax expense
Current	94,254	89,340	74,039
Deferred	30,597	5,603	17,653
Total income tax expense	124,851	94,943	91,692
Earnings from continuing operations	422,406	232,914	207,146
Loss on discontinued operations, net of tax (Note 2)	(2,915)	(11,737)	(2,223)
Net earnings	419,491	221,177	204,923
Other comprehensive income (loss), net of tax
Reclassification adjustment for cash flow hedges	1,194	5,828	4,856
Adjustment for funded status of benefit plans	(20,583)	23,832	(69,051)
Amortization of actuarial loss and prior service cost for benefit plans	82	11,985	2,112
Other comprehensive income (loss)	(19,307)	41,645	(62,083)
Comprehensive income	$ 400,184	$ 262,822	$ 142,840
Basic earnings (loss) per share
Continuing operations	$ 3.17	$ 1.75	$ 1.58
Discontinued operations	(0.02)	(0.09)	(0.02)
Net earnings	3.15	1.66	1.56
Diluted earnings (loss) per share
Continuing operations	3.11	1.72	1.56
Discontinued operations	(0.02)	(0.08)	(0.02)
Net earnings	$ 3.09	$ 1.64	$ 1.54
Weighted-average common shares outstanding
Basic	133,205	133,210	131,461
Assuming dilution	135,790	135,093	132,991