Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Statement [Abstract]
Net sales	$ 821,175	$ 968,372	$ 2,770,000	$ 2,760,673
Cost of sales	648,996	821,305	2,223,288	2,278,927
Gross profit	172,179	147,067	546,712	481,746
Selling, general and administrative expenses	29,662	29,736	87,592	85,409
Income (loss) from operations	142,517	117,331	459,120	396,337
Other income (expense)
Interest expense	(11,934)	(12,727)	(35,682)	(38,449)
Debt retirement costs	(7,082)	0	(7,082)	0
Gain from sales of equity securities	477	0	16,429	0
Other income, net	1,222	1,457	3,676	4,296
Income before income taxes	125,200	106,061	436,461	362,184
Provision for income taxes	38,236	38,131	146,183	129,661
Net income (loss)	$ 86,964	$ 67,930	$ 290,278	$ 232,523
Earnings per share:
Basic	$ 1.30	$ 1.02	$ 4.36	$ 3.50
Diluted	$ 1.30	$ 1.01	$ 4.33	$ 3.48
Weighted average shares outstanding:
Basic	66,311,958	66,012,102	66,240,225	65,919,892
Diluted	66,656,760	66,381,932	66,621,520	66,307,604
Dividends per common share	$ 0.1875	$ 0.0738	$ 0.3350	$ 0.2008