Derivative Commodity Instruments Derivative Commodity instruments not designated as hedging instruments on the Income Statement (Details) (Gain (loss) on derivative instruments, net, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Gain (loss) on derivative instruments, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in income on derivatives	$ (90,581)	$ 53,078	$ (148,026)	$ 21,577