Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Net income	$ 27,651	$ 37,172	$ 86,474	$ 101,968
Other comprehensive income (loss):
Pension adjustments, net of tax	806	742	2,416	2,226
Total other comprehensive income	1,180	825	4,036	2,789
Total comprehensive income	28,831	37,997	90,510	104,757
Natural Gas Swap [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	49	83	(12)	404
Corn Option [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	325	0	1,632	0
Interest Rate Swap [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	$ 0	$ 0	$ 0	$ 159