Derivatives (Impact of Cash Flow Hedges Table) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Price Risk Cash Flow Hedges [Abstract]
Liquids realized loss included in Midstream revenue	$ 456	$ (527)	$ 851	$ (2,235)

The amount of net gains or losses on price risk cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income.

No definition available.

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