Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Net sales	$ 939,047	$ 913,958	$ 1,803,694	$ 1,948,825
Cost of sales	665,560	712,062	1,302,398	1,574,292
Gross profit	273,487	201,896	501,296	374,533
Selling, general and administrative expenses	38,260	30,918	72,014	57,930
Income from operations	235,227	170,978	429,282	316,603
Other income (expense)
Interest expense	(5,343)	(11,571)	(11,624)	(23,748)
Gain from sales of equity securities	0	15,952	0	15,952
Other income, net	(95)	1,107	3,424	2,454
Income before income taxes	229,789	176,466	421,082	311,261
Provision for income taxes	83,973	60,965	151,919	107,947
Net income	$ 145,816	$ 115,501	$ 269,163	$ 203,314
Earnings per share:
Basic	$ 2.18	$ 1.73	$ 4.02	$ 3.05
Diluted	$ 2.17	$ 1.72	$ 4.01	$ 3.03
Weighted average shares outstanding:
Basic	66,629,609	66,298,633	66,627,661	66,203,965
Diluted	66,895,595	66,648,896	66,902,273	66,603,706
Dividends per common share	$ 0.1875	$ 0.0738	$ 0.3750	$ 0.1475