Derivatives (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended
Dec. 31, 2012	Mar. 31, 2013 Commodity Futures Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives scheduled to mature		September 2014
Cash flow hedge derivative gains (losses) expected to be reclassified into earnings within the next 12 months		$ 1.9
Derivatives (Textual) [Abstract]
Hedged value of revolving credit facility	$ 100
Variable Interest Rate Swap Expiration Date	Oct. 12, 2012
Variable portion of the interest rate swap tied	1-Month LIBOR

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80748-113994

Reference 2: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Name:	us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration