Summary of Significant Accounting Policies, Derivatives by Hedging Relationship and Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified											3 Months Ended		9 Months Ended
	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 1 Quoted Prices [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Level 1 Quoted Prices [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 2 Observable [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Level 2 Observable [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Level 3 Unobservable [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Unobservable [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Counterparty Offsets [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Counterparty Offsets [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Total Fair Value [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Total Fair Value [Member]	Sep. 30, 2013 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Sep. 30, 2012 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Sep. 30, 2013 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Sep. 30, 2012 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]
Earnings (loss) recognized in income [Abstract]
Earnings (Loss)											$ (103)	$ (1,562)	$ (105)	$ (2,555)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Current assets	0	299	555	389	0	0	0	(270)	555	418
Derivatives - Current liabilities	0	0	(39)	(682)	0	0	0	270	(39)	(412)
Net Value	$ 0	$ 299	$ 516	$ (293)	$ 0	$ 0	$ 0	$ 0	$ 516	$ 6