Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
Net sales	$ 462,701	$ 480,233	$ 473,572	$ 457,798	$ 466,391	$ 501,125	$ 494,627	$ 465,830	$ 1,874,304	$ 1,927,973	$ 1,372,965
Costs and expenses:
Cost of sales	(396,428)	(409,822)	(398,546)	(403,076)	(405,325)	(448,927)	(433,358)	(414,920)	(1,607,872)	(1,702,530)	(1,173,804)
Selling, general and administrative expenses	(30,793)	(30,649)	(30,529)	(29,074)	(28,343)	(26,815)	(27,476)	(27,364)	(121,045)	(109,998)	(100,394)
Total operating costs and expenses	(427,221)	(440,471)	(429,075)	(432,150)	(433,668)	(475,742)	(460,834)	(442,284)	(1,728,917)	(1,812,528)	(1,274,198)
Income from operations	35,480	39,762	44,497	25,648	32,723	25,383	33,793	23,546	145,387	115,445	98,767
Interest expense, net									(33,796)	(44,809)	(22,571)
Other, net									0	284	0
Earnings before income taxes									111,591	70,920	76,196
Income tax provision									(47,460)	(31,246)	(2,396)
Net earnings	$ 19,852	$ 19,064	$ 21,489	$ 3,726	$ 11,502	$ 8,645	$ 13,923	$ 5,604	$ 64,131	$ 39,674	$ 73,800
Net earnings per common share:
Basic (in dollars per share)	$ 0.86	$ 0.82	$ 0.92	$ 0.16	$ 0.51	$ 0.38	$ 0.60	$ 0.25	$ 2.75	$ 1.73	$ 3.22
Diluted (in dollars per share)	$ 0.84	$ 0.80	$ 0.91	$ 0.16	$ 0.48	$ 0.37	$ 0.59	$ 0.24	$ 2.72	$ 1.66	$ 3.12