Derivatives (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Oct. 01, 2011
MMBTUs covered by natural gas swaps	4,200,000
Natural Gas Forward Purchase Contracts [Member]
Net deferred losses on cash flow hedges on natural gas forward purchase contracts that are included in accumulated other comprehensive income that are expected to be reclassified into earnings during the next twelve months	$ 39.6
Net deferred losses on cash flow hedges reclassification period	within the next 12 months

Description of the transactions or other events that will result in the reclassification into earnings of gains or losses reported in accumulated other comprehensive income. May include the time period over which gains or losses will be reclassified to earnings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph b(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6887037&loc=d3e80748-113994

Name:	us-gaap_DescriptionOfReclassificationOfCashFlowHedgeGainLoss
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration