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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net sales	$ 845,440	$ 723,473	$ 2,400,877	$ 2,107,298
Cost of sales	(619,626)	(560,921)	(1,800,509)	(1,641,619)
Gross profit	225,814	162,552	600,368	465,679
Selling and administrative expenses	(56,469)	(51,529)	(167,009)	(156,339)
Corporate overhead	(21,143)	(16,990)	(59,852)	(51,614)
Alternative fuel mixture credits				95,500
Other expense, net	(6,242)	(1,961)	(21,031)	(8,186)
Income from operations	141,960	92,072	352,476	345,040
Interest expense, net	(11,850)	(30,590)	(30,333)	(53,529)
Income before taxes	130,110	61,482	322,143	291,511
Provision for income taxes	(45,930)	(21,691)	(112,885)	(188,722)
Net income	84,180	39,791	209,258	102,789
Weighted average common shares outstanding:
Basic	96,758	96,360	96,536	96,408
Diluted	97,597	97,349	97,512	97,520
Net income per common share:
Basic	$ 0.87	$ 0.41	$ 2.17	$ 1.07
Diluted	$ 0.86	$ 0.41	$ 2.15	$ 1.05
Dividends declared per common share	$ 0.40	$ 0.25	$ 1.1125	$ 0.7500
Net income	84,180	39,791	209,258	102,789
Other comprehensive income (loss), net of tax:
Fair value adjustments to cash flow hedges				(10,183)
Reclassification adjustment for cash flow hedges included in net income	870	(605)	2,609	977
Amortization of pension and postretirement plans actuarial loss and prior service cost	3,387	1,672	11,921	5,016
Unfunded employee benefit obligations	4,963		13,418
Other comprehensive income	9,220	1,067	27,948	(4,190)
Comprehensive income	$ 93,400	$ 40,858	$ 237,206	$ 98,599