Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Net income	$ 26,418	$ 36,225	$ 58,823	$ 64,796
Other comprehensive income (loss):
Pension adjustments, net of tax	805	742	1,610	1,484
Total other comprehensive income	954	1,073	2,856	1,964
Total comprehensive income	27,372	37,298	61,679	66,760
Natural Gas Swap [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	(209)	314	(61)	321
Corn Option [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	358	0	1,307	0
Interest Rate Swap [Member]
Other comprehensive income (loss):
Derivative adjustments, net of tax	$ 0	$ 17	$ 0	$ 159