Consolidated Statements of Stockholders’ Equity and Comprehensive Income(Loss) (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balance at Jan. 03, 2009	$ 236,578	$ 822	$ 156,899	$ (3,848)	$ (29,850)	$ 112,555
Balance (in shares) at Jan. 03, 2009		81,767,982
Net income	41,790					41,790
Pension liability adjustments, net of tax	5,229				5,229
Interest rate swap derivative adjustment, net of tax	702				702
Natural gas swap derivative adjustment, net of tax	137				137
Total comprehensive income	47,858
Issuance of non-vested stock (in shares)		307,558
Issuance of non-vested stock	904	3	901
Stock-based compensation	(720)		(720)
Tax benefits associated with stock-based compensation	(39)		(39)
Treasury stock (in shares)		(2,186)
Treasury stock	(7)			(7)
Issuance of common stock (in shares)		153,336
Issuance of common stock	303	1	302
Balance at Jan. 02, 2010	284,877	826	157,343	(3,855)	(23,782)	154,345
Balance (in shares) at Jan. 02, 2010		82,226,690
Net income	44,243					44,243
Pension liability adjustments, net of tax	2,346				2,346
Interest rate swap derivative adjustment, net of tax	507				507
Natural gas swap derivative adjustment, net of tax	(59)				(59)
Total comprehensive income	47,037
Issuance of non-vested stock (in shares)		254,220
Issuance of non-vested stock	2,404	3	2,401
Stock-based compensation	94		94
Tax benefits associated with stock-based compensation	234		234
Treasury stock (in shares)		(51,740)
Treasury stock	(485)			(485)
Issuance of common stock (in shares)		10,130,501
Issuance of common stock	130,135	101	130,034
Balance at Jan. 01, 2011	464,296	930	290,106	(4,340)	(20,988)	198,588
Balance (in shares) at Jan. 01, 2011		92,559,671
Net income	169,418					169,418
Pension liability adjustments, net of tax	(10,146)				(10,146)
Interest rate swap derivative adjustment, net of tax	712				712
Natural gas swap derivative adjustment, net of tax	(482)				(482)
Total comprehensive income	159,502
Issuance of non-vested stock (in shares)		174,285
Issuance of non-vested stock	2,540	2	2,538
Stock-based compensation	492		492
Tax benefits associated with stock-based compensation	1,125		1,125
Treasury stock (in shares)		(88,364)
Treasury stock	(1,248)			(1,248)
Issuance of common stock (in shares)		24,402,846
Issuance of common stock	293,668	244	293,424
Balance at Dec. 31, 2011	$ 920,375	$ 1,176	$ 587,685	$ (5,588)	$ (30,904)	$ 368,006
Balance (in shares) at Dec. 31, 2011		117,048,438