CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net earnings	$ 601,185	$ 419,491	$ 221,177
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	305,965	284,940	274,823
Net gain on sale of property, plant & equipment and businesses	(17,827)	(15,431)	(9,927)
Contributions to pension plans	(20,023)	(9,576)	(14,047)
Share-based compensation expense	26,635	20,670	18,248
Excess tax benefits from share-based compensation	0	0	(18,376)
Deferred tax expense (benefit)	(235,697)	33,591	3,069
Cost of debt purchase	140,772	0	67,075
(Increase) decrease in assets excluding the initial effects of business acquisitions and dispositions
Accounts and notes receivable	(81,561)	(72,763)	(42,164)
Inventories	(14,121)	1,625	(20,925)
Prepaid expenses	(28,445)	2,558	(5,288)
Other assets	(23,759)	(18,236)	34,863
Increase (decrease) in liabilities excluding the initial effects of business acquisitions and dispositions
Accrued interest and income taxes	1,303	(7,187)	26,605
Trade payables and other accruals	9,823	30,353	26,491
Other noncurrent liabilities	(32,592)	(29,138)	(42,702)
Other, net	13,020	3,691	616
Net cash provided by operating activities	644,678	644,588	519,538
Investing Activities
Purchases of property, plant & equipment	(459,566)	(350,148)	(289,262)
Proceeds from sale of property, plant & equipment	15,756	23,318	8,218
Proceeds from sale of businesses, net of transaction costs	287,292	0	0
Payment for businesses acquired, net of acquired cash	(1,109,725)	(32,537)	(27,198)
Other, net	(3,248)	2,173	(350)
Net cash used for investing activities	(1,269,491)	(357,194)	(308,592)
Financing Activities
Proceeds from short-term debt	5,000	3,000	441,000
Payment of short-term debt	(5,000)	(3,000)	(206,000)
Payment of current maturities and long-term debt	(1,463,308)	(130)	(695,060)
Proceeds from issuance of long-term debt	2,200,000	0	400,000
Debt discounts and issuance costs	(15,291)	(1,860)	(7,382)
Purchases of common stock	(60,303)	(161,463)	(21,475)
Dividends paid	(132,335)	(106,333)	(53,214)
Proceeds from exercise of stock options	0	0	72,971
Share-based compensation, shares withheld for taxes	(25,323)	(34,799)	(16,225)
Excess tax benefits from share-based compensation	0	0	18,376
Net cash provided by (used for) financing activities	503,440	(304,585)	(67,009)
Net increase (decrease) in cash and cash equivalents and restricted cash	(121,373)	(17,191)	143,937
Cash and cash equivalents and restricted cash at beginning of year	268,019	285,210	141,273
Cash and cash equivalents and restricted cash at end of year	$ 146,646	$ 268,019	$ 285,210