Other Assets (Narr) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other Assets Noncurrent [Line Items]
Debt issuance costs Senior Notes and Revolver	$ 30,599	$ 23,460
[TwoThousandAndEightNotesAndRevolvingCreditFacilityMember]
Other Assets Noncurrent [Line Items]
Debt issuance costs Senior Notes and Revolver	32,200
[SmEnergyLitigationMember]
Other Assets Noncurrent [Line Items]
Deposits related to SM Energy litigation	$ 6,000	$ 6,000