Segment Information (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Operating income (loss)
Profit sharing									$ (43,149,000)	$ (25,476,000)	$ (2,980,000)
Operating income	82,490,000	108,785,000	188,219,000	205,326,000	46,821,000	69,000,000	116,635,000	132,297,000	584,820,000	364,753,000	119,531,000
Assets
Cash and equivalents	390,761,000				186,513,000				390,761,000	186,513,000	9,008,000	16,233,000
Investment in short-term commercial paper	84,830,000								84,830,000
Income taxes receivable	16,722,000				37,311,000				16,722,000	37,311,000
Deferred income taxes	25,341,000				20,684,000				25,341,000	20,684,000
Property, plant and equipment, net	2,193,745,000				2,213,333,000				2,193,745,000	2,213,333,000
Other	134,264,000				135,683,000				134,264,000	135,683,000
Total assets	5,979,226,000				5,589,934,000				5,979,226,000	5,589,934,000	5,129,872,000
Liabilities
Accounts payable	420,824,000				348,601,000				420,824,000	348,601,000
Income taxes payable	10,880,000				5,227,000				10,880,000	5,227,000
Accrued interest	36,265,000				35,416,000				36,265,000	35,416,000
Debt	2,380,100,000				2,386,821,000				2,380,100,000	2,386,821,000
Deferred income taxes	489,915,000				457,432,000				489,915,000	457,432,000
Liabilities	3,608,632,000				3,458,804,000				3,608,632,000	3,458,804,000	3,126,607,000
Other
Operating income (loss)
Corporate SG and A									(46,700,000)	(31,600,000)	(26,500,000)
Company-wide stock option expense									(14,800,000)	(12,500,000)	(13,200,000)
Profit sharing									(35,100,000)	(21,100,000)	(2,200,000)
Other, net									1,500,000	(1,000,000)	(3,500,000)
Operating income									(95,141,000)	(66,189,000)	(45,356,000)
Assets
Cash and equivalents	314,900,000				175,300,000				314,900,000	175,300,000
Investment in short-term commercial paper	84,800,000								84,800,000
Income taxes receivable	16,700,000				37,300,000				16,700,000	37,300,000	137,000,000
Deferred income taxes	25,300,000				20,700,000				25,300,000	20,700,000	21,500,000
Property, plant and equipment, net	85,700,000				70,700,000				85,700,000	70,700,000	44,500,000
Debt issuance costs	23,900,000				23,300,000				23,900,000	23,300,000	24,000,000
Intra-company debt	152,800,000				134,800,000				152,800,000	134,800,000	174,900,000
Other	85,200,000				100,900,000				85,200,000	100,900,000	67,500,000
Total assets	789,322,000				562,961,000				789,322,000	562,961,000	469,389,000
Liabilities
Accounts payable	28,700,000				32,500,000				28,700,000	32,500,000	37,800,000
Income taxes payable	11,100,000				5,200,000				11,100,000	5,200,000	5,700,000
Accrued interest	33,700,000				33,700,000				33,700,000	33,700,000	27,300,000
Accrued profit sharing	35,800,000				21,500,000				35,800,000	21,500,000	2,300,000
Debt	2,341,900,000				2,341,000,000				2,341,900,000	2,341,000,000	2,158,200,000
Deferred income taxes	217,600,000				242,700,000				217,600,000	242,700,000	220,900,000
Other liabilities	91,100,000				70,200,000				91,100,000	70,200,000	62,200,000
Liabilities	$ 2,759,894,000				$ 2,746,798,000				$ 2,759,894,000	$ 2,746,798,000	$ 2,514,423,000