CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities
Net earnings (loss)	$ 24,382,000	$ (52,593,000)	$ (70,778,000)
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	307,108,000	331,959,000	361,719,000
Net gain on sale of property, plant & equipment and businesses	(50,978,000)	(78,654,000)	(58,808,000)
Contributions to pension plans	(4,855,000)	(4,509,000)	(4,892,000)
Share-based compensation	22,093,000	17,474,000	18,454,000
Excess tax benefits from share-based compensation	(161,000)	(267,000)	(121,000)
Deferred tax provision (benefit)	(35,063,000)	(69,830,000)	(93,739,000)
Cost of debt purchase	0	0	19,153,000
(Increase) decrease in assets before initial effects of business acquisitions and dispositions
Accounts and notes receivable	(42,260,000)	17,412,000	5,035,000
Inventories	(7,700,000)	(9,028,000)	(6,927,000)
Prepaid expenses	(765,000)	(117,000)	(1,354,000)
Other assets	12,374,000	(29,043,000)	7,673,000
Increase (decrease) in liabilities before initial effects of business acquisitions and dispositions
Accrued interest and income taxes	(10,937,000)	(15,709,000)	5,831,000
Trade payables and other accruals	15,485,000	27,091,000	(27,871,000)
Proceeds from sale of future production, net of transaction costs (Note 19)	153,095,000	73,583,000	0
Other noncurrent liabilities	(26,602,000)	29,772,000	5,707,000
Other, net	1,283,000	934,000	9,961,000
Net cash provided by operating activities	356,499,000	238,475,000	169,043,000
Investing Activities
Purchases of property, plant & equipment	(275,380,000)	(93,357,000)	(98,912,000)
Proceeds from sale of property, plant & equipment	17,576,000	80,829,000	13,675,000
Proceeds from sale of businesses, net of transaction costs	51,604,000	21,166,000	74,739,000
Payment for businesses acquired, net of acquired cash	(89,951,000)	0	(10,531,000)
Other, net	(39,000)	1,761,000	1,550,000
Net cash provided by (used for) investing activities	(296,190,000)	10,399,000	(19,479,000)
Financing Activities
Proceeds from line of credit	156,000,000	0	0
Payment of current maturities of long-term debt & line of credit	(306,602,000)	(134,780,000)	(1,028,575,000)
Cost of debt purchase	0	0	(19,153,000)
Proceeds from issuance of long-term debt, net of discounts	0	0	1,100,000,000
Debt issuance costs	0	0	(27,426,000)
Proceeds from settlement of interest rate swap agreements	0	0	23,387,000
Proceeds from issuance of common stock	3,821,000	0	4,936,000
Dividends paid	(5,191,000)	(5,183,000)	(98,172,000)
Proceeds from exercise of stock options	9,762,000	10,462,000	3,615,000
Excess tax benefits from share-based compensation	161,000	267,000	121,000
Other, net	0	(1,000)	1,000
Net cash used for financing activities	(142,049,000)	(129,235,000)	(41,266,000)
Net increase (decrease) in cash and cash equivalents	(81,740,000)	119,639,000	108,298,000
Cash and cash equivalents at beginning of year	275,478,000	155,839,000	47,541,000
Cash and cash equivalents at end of period	$ 193,738,000	$ 275,478,000	$ 155,839,000