Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating Activities
Net earnings (loss)	$ 15,300,000	$ (56,076,000)
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	230,877,000	253,391,000
Net gain on sale of property, plant & equipment and businesses	(48,597,000)	(31,886,000)
Proceeds from sale of future production, net of transactions costs (Note 16)	153,095,000	0
Contributions to pension plans	(3,535,000)	(3,379,000)
Share-based compensation	16,789,000	9,362,000
Deferred tax provision	(25,862,000)	(66,194,000)
Changes in assets and liabilities before initial effects of business acquisitions and dispositions	(78,947,000)	(9,886,000)
Other, net	892,000	(1,573,000)
Net cash provided by operating activities	260,012,000	93,759,000
Investing Activities
Purchases of property, plant & equipment	(117,310,000)	(49,418,000)
Proceeds from sale of property, plant & equipment	14,974,000	28,930,000
Proceeds from sale of businesses, net of transaction costs	51,604,000	10,690,000
Payment for businesses acquired, net of acquired cash	(89,951,000)	0
Other, net	2,000	963,000
Net cash used for investing activities	(140,681,000)	(8,835,000)
Financing Activities
Proceeds from line of credit	156,000,000	0
Payment of current maturities of long-term debt & line of credit	(306,493,000)	(120,000)
Dividends paid	(3,890,000)	(3,885,000)
Proceeds from exercise of stock options	4,491,000	6,167,000
Other, net	896,000	201,000
Net cash provided by (used for) financing activities	(148,996,000)	2,363,000
Net increase (decrease) in cash and cash equivalents	(29,665,000)	87,287,000
Cash and cash equivalents at beginning of year	275,478,000	155,839,000
Cash and cash equivalents at end of period	$ 245,813,000	$ 243,126,000