Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) earnings	$ (97,265,000)	$ 676,000	$ (21,698,000)
Provision for depreciation, depletion, and amortization	82,048,000	47,642,000	55,815,000
Credit for losses on accounts receivable	(100,000)	(165,000)	(201,000)
Loss on early extinguishment of debt			666,000
Gain on sale of business		(12,515,000)
Loss (gain) on sale of assets	882,000	(960,000)	(36,202,000)
Impairment of long-lived assets	64,548,000	2,075,000	58,837,000
Non-cash inventory, spare parts and other writedowns	6,653,000		13,093,000
Compensation expense for stock-based awards	1,773,000	2,021,000	3,016,000
Deferred income taxes	(25,373,000)	(2,077,000)	(23,269,000)
Changes in operating assets and liabilities:
Receivables	(972,000)	21,726,000	6,432,000
Inventories	(2,393,000)	18,235,000	18,965,000
Other assets	(22,793,000)	(20,568,000)	(17,608,000)
Accounts payable and other liabilities	(9,469,000)	(11,153,000)	(1,558,000)
Accrued and refundable income taxes	806,000	(9,009,000)	8,196,000
Net cash (used in) provided by operating activities	(1,655,000)	35,928,000	64,484,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(37,466,000)	(149,424,000)	(78,063,000)
Grants received for capital expenditures		236,000	610,000
Proceeds from sale of business	105,067,000	20,817,000
Proceeds from sale of assets	1,243,000	7,194,000	43,830,000
Net cash provided by (used in) investing activities	68,844,000	(121,177,000)	(33,623,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net issuances (payments) of commercial paper	(40,700,000)	32,050,000	(14,590,000)
Borrowings under credit agreements	65,000,000	8,500,000	36,250,000
Payments under credit agreements	(70,500,000)	(3,000,000)	(36,250,000)
Issuances of notes payable		50,000,000	50,000,000
Payments of notes payable			(35,000,000)
Payments of industrial development bond agreement		(19,000,000)
Payment of premium on early extinguishment of debt	0		(708,000)
Dividends paid	(5,929,000)	(5,918,000)	(5,905,000)
Proceeds from stock option exercises	490,000
Net cash (used in) provided by financing activities	(51,639,000)	62,632,000	(6,203,000)
Net increase (decrease) in cash and cash equivalents	15,550,000	(22,617,000)	24,658,000
Cash and cash equivalents at beginning of year	4,044,000	26,661,000	2,003,000
Cash and cash equivalents at end of year	19,594,000	4,044,000	26,661,000
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid - net of amount capitalized	7,606,000	2,012,000	5,677,000
Income taxes paid	224,000	3,145,000	1,176,000
Noncash investing activities:
Capital expenditures	7,100,000	4,700,000	20,300,000
Capital expenditure grants included within receivables	$ 1,000,000