CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net earnings (loss)	$ 204,923	$ 24,382	$ (52,593)
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	279,497	307,108	331,959
Net gain on sale of property, plant & equipment and businesses	(244,222)	(50,978)	(78,654)
Proceeds from sale of future production, net of transactions costs (Note 19)	0	153,095	73,583
Contributions to pension plans	(5,488)	(4,855)	(4,509)
Share-based compensation	23,884	22,093	17,474
Excess tax benefits from share-based compensation	(3,464)	(161)	(267)
Deferred tax provision (benefit)	18,378	(35,063)	(69,830)
Cost of debt purchase	72,949	0	0
(Increase) decrease in assets before initial effects of business acquisitions and dispositions
Accounts and notes receivable	(25,118)	(42,260)	17,412
Inventories	(5,595)	(7,700)	(9,028)
Prepaid expenses	(6,256)	(765)	(117)
Other assets	(13,930)	12,374	(29,043)
Increase (decrease) in liabilities before initial effects of business acquisitions and dispositions
Accrued interest and income taxes	(3,840)	(10,937)	(15,709)
Trade payables and other accruals	4,229	15,485	27,091
Other noncurrent liabilities	(42,810)	(26,602)	29,772
Other, net	7,199	1,283	934
Net cash provided by operating activities	260,336	356,499	238,475
Investing Activities
Purchases of property, plant & equipment	(224,852)	(275,380)	(93,357)
Proceeds from sale of property, plant & equipment	26,028	17,576	80,829
Proceeds from sale of businesses, net of transaction costs	721,359	51,604	21,166
Payment for businesses acquired, net of acquired cash	(284,237)	(89,951)	0
Other, net	33	(39)	1,761
Net cash provided by (used for) investing activities	238,331	(296,190)	10,399
Financing Activities
Proceeds from line of credit	93,000	156,000	0
Payment of current maturities, long-term debt and line of credit	(672,829)	(306,602)	(134,780)
Proceeds from issuance of common stock	30,620	3,821	0
Dividends paid	(28,884)	(5,191)	(5,183)
Proceeds from exercise of stock options	23,502	9,762	10,462
Excess tax benefits from share-based compensation	3,464	161	267
Other, net	(5)	0	(1)
Net cash used for financing activities	(551,132)	(142,049)	(129,235)
Net increase (decrease) in cash and cash equivalents	(52,465)	(81,740)	119,639
Cash and cash equivalents at beginning of year	193,738	275,478	155,839
Cash and cash equivalents at end of period	$ 141,273	$ 193,738	$ 275,478