Summary of Significant Accounting Policies, Derivatives by Hedging Relationship and Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified											3 Months Ended		6 Months Ended
	Jun. 30, 2012 Level 1 Quoted Prices [Member]	Dec. 31, 2011 Level 1 Quoted Prices [Member]	Jun. 30, 2012 Level 2 Observable [Member]	Dec. 31, 2011 Level 2 Observable [Member]	Jun. 30, 2012 Level 3 Unobservable [Member]	Dec. 31, 2011 Level 3 Unobservable [Member]	Jun. 30, 2012 Counterparty offsets [Member]	Dec. 31, 2011 Counterparty offsets [Member]	Jun. 30, 2012 Total Fair Value [Member]	Dec. 31, 2011 Total Fair Value [Member]	Jun. 30, 2012 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Jun. 30, 2011 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Jun. 30, 2012 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]	Jun. 30, 2011 Commodity Contract [Member] Revenues - marketing [Member] Not Designated as Hedging Instrument [Member]
Earnings (loss) recognized in income [Abstract]
Earnings (Loss)											$ 1,889	$ (306)	$ (993)	$ 508
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Forward Hydrocarbon Commodity Contracts - Current assets	0	1,455	4,426	2,045	0	0	(3,416)	(1,436)	1,010	2,064
Derivatives - Forward Hydrocarbon Commodity Contracts - Current liabilities	(513)	(675)	(3,523)	(1,442)	0	0	3,416	1,436	(620)	(681)
Net Value	$ (513)	$ 780	$ 903	$ 603	$ 0	$ 0	$ 0	$ 0	$ 390	$ 1,383