Summary of Significant Accounting Policies, Derivatives by Hedging Relationship and Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified											3 Months Ended
	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Level 1 Quoted Prices [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 1 Quoted Prices [Member]	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Level 2 Observable [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 2 Observable [Member]	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Level 3 Unobservable [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Level 3 Unobservable [Member]	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Counterparty Offsets [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Counterparty Offsets [Member]	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Total Fair Value [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Total Fair Value [Member]	Mar. 31, 2014 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]
Earnings (loss) recognized in income [Abstract]
Earnings (Loss)											$ 398	$ 150
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Current assets	0	0	143	449	0	0	(45)	(54)	98	395
Derivatives - Current liabilities	0	0	(64)	(54)	0	0	45	54	(19)	0
Net Value	$ 0	$ 0	$ 79	$ 395	$ 0	$ 0	$ 0	$ 0	$ 79	$ 395