Condensed Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net sales	$ 723,473	$ 670,824	$ 2,107,298	$ 1,965,805
Cost of sales	(560,921)	(533,077)	(1,641,619)	(1,558,016)
Gross profit	162,552	137,747	465,679	407,789
Selling and administrative expenses	(51,529)	(48,914)	(156,339)	(145,058)
Corporate overhead	(16,990)	(16,424)	(51,614)	(48,329)
Alternative fuel mixture credits			95,500
Other expense, net	(1,961)	(1,229)	(8,186)	(9,460)
Income from operations	92,072	71,180	345,040	204,942
Interest expense, net	(30,590)	(6,727)	(53,529)	(19,951)
Income before taxes	61,482	64,453	291,511	184,991
Provision for income taxes	(21,691)	(22,676)	(188,722)	(66,429)
Net income	39,791	41,777	102,789	118,562
Weighted average common shares outstanding:
Basic	96,360	99,020	96,408	99,945
Diluted	97,349	100,030	97,520	101,030
Net income per common share:
Basic	$ 0.41	$ 0.42	$ 1.07	$ 1.19
Diluted	$ 0.41	$ 0.42	$ 1.05	$ 1.17
Dividends declared per common share	$ 0.25	$ 0.20	$ 0.75	$ 0.60
Other comprehensive income (loss), net of tax:
Fair value adjustments to cash flow hedges		(25,468)	(10,183)	(19,746)
Reclassification adjustment for cash flow hedges included in net income	(605)	(283)	977	(846)
Amortization of pension and postretirement plans actuarial loss and prior service cost	1,672	951	5,016	2,853
Other comprehensive income (loss)	1,067	(24,800)	(4,190)	(17,739)
Comprehensive income	$ 40,858	$ 16,977	$ 98,599	$ 100,823