Derivative Financial Instruments (Details 2) (Derivatives in Fair Value Hedging Relationships, Cost of sales, USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Futures contracts
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 26,176	$ 16,373
Inventories
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Hedged Items	$ (23,621)	$ (16,209)

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

Name:	us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration