Derivatives (Impact of Cash Flow Hedges Table) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Price Risk Cash Flow Hedges [Abstract]
Liquids realized loss included in Midstream revenue	$ (280)	$ 12

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