Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011
Summary of net gains and losses
Total Net Gain (Loss)	$ 0	$ (1,055)	$ 0	$ (1,017)
Fuel hedges [Member] | Contract premium and contract settlement [Member] | S,D&A expenses [Member]
Summary of net gains and losses
Total Net Gain (Loss)	0	(105)	0	66
Fuel hedges [Member] | Mark-to-market adjustment [Member] | S,D&A expenses [Member]
Summary of net gains and losses
Total Net Gain (Loss)	0	(25)	0	(171)
Aluminum hedges [Member] | Contract premium and contract settlement [Member] | Cost of sales [Member]
Summary of net gains and losses
Total Net Gain (Loss)	0	783	0	1,304
Aluminum hedges [Member] | Mark-to-market adjustment [Member] | Cost of sales [Member]
Summary of net gains and losses
Total Net Gain (Loss)	$ 0	$ (1,708)	$ 0	$ (2,216)