Segment Information (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Operating income (loss)
Profit sharing	$ (8,211,000)	$ (14,454,000)	$ (16,283,000)	$ (29,657,000)
Operating income	103,699,000	188,219,000	223,515,000	393,545,000
Assets
Cash and equivalents	420,938,000	277,691,000	420,938,000	277,691,000	357,809,000	390,761,000	160,810,000	186,513,000
Investments in short-term commercial paper	9,998,000		9,998,000			84,830,000
Income taxes receivable	17,082,000		17,082,000			16,722,000
Deferred income taxes	26,917,000		26,917,000			25,341,000
Property, plant and equipment, net	2,208,660,000		2,208,660,000			2,193,745,000
Other	129,000,000		129,000,000			134,264,000
Total assets	5,971,380,000	5,900,453,000	5,971,380,000	5,900,453,000		5,979,226,000
Liabilities
Accounts payable	393,174,000		393,174,000			420,824,000
Income taxes payable	2,164,000		2,164,000			10,880,000
Deferred income taxes	510,479,000		510,479,000			489,915,000
Liabilities	3,539,820,000	3,588,965,000	3,539,820,000	3,588,965,000
Other
Operating income (loss)
Corporate SG and A	(7,200,000)	(10,000,000)	(14,800,000)	(19,300,000)
Company-wide stock option expense	(2,000,000)	(3,700,000)	(5,700,000)	(7,400,000)
Profit sharing	(5,900,000)	(11,900,000)	(12,400,000)	(25,200,000)
Other, net	400,000	200,000	1,400,000	2,200,000
Operating income	(14,673,000)	(25,422,000)	(31,535,000)	(49,678,000)
Assets
Cash and equivalents	309,200,000	265,600,000	309,200,000	265,600,000
Investments in short-term commercial paper	10,000,000		10,000,000
Income taxes receivable	17,100,000	15,300,000	17,100,000	15,300,000
Deferred income taxes	26,900,000	21,100,000	26,900,000	21,100,000
Property, plant and equipment, net	83,900,000	69,900,000	83,900,000	69,900,000
Debt issuance costs, net	22,300,000	21,000,000	22,300,000	21,000,000
Intra-company debt	170,600,000	153,700,000	170,600,000	153,700,000
Other	85,700,000	85,600,000	85,700,000	85,600,000
Total assets	725,717,000	632,242,000	725,717,000	632,242,000
Liabilities
Accounts payable	28,700,000	35,400,000	28,700,000	35,400,000
Income taxes payable	2,900,000	11,600,000	2,900,000	11,600,000
Accrued interest	31,000,000	33,700,000	31,000,000	33,700,000
Accrued profit sharing	12,600,000	25,800,000	12,600,000	25,800,000
Debt	2,330,000,000	2,340,900,000	2,330,000,000	2,340,900,000
Deferred income taxes	213,000,000	227,000,000	213,000,000	227,000,000
Other liabilities	81,500,000	65,800,000	81,500,000	65,800,000
Liabilities	$ 2,699,661,000	$ 2,740,245,000	$ 2,699,661,000	$ 2,740,245,000