Other Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other Assets Noncurrent [Line Items]
Debt issuance costs	$ 30,599	$ 23,460
Reimbursement Agreement Deferred Issuance Costs	11,290	0
Other	2,017	924
Total other assets	49,906	30,384
[SmEnergyLitigationMember]
Other Assets Noncurrent [Line Items]
Deposits related to SM Energy litigation	$ 6,000	$ 6,000