Related Party Transactions (Changes In The Affiliate Payable/Receivables Balance) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 28, 2012		Oct. 03, 2011
Related Party Transactions [Abstract]
Net affiliate receivable, beginning balance	$ 3,734,000		$ (442,000)
Revenues and other increases	256,496,000	[1]	130,946,000	[1],[2]
Expenditures	(208,780,000)		(70,367,000)
Settlements from the Fund	(51,450,000)		(56,403,000)
Net affiliate payable, ending balance			3,734,000
Overhead producing expenses	(3,700,000)		(1,600,000)
Proceeds from the sale of oil and gas leases			1,300,000
Purchase price adjustments					$ 5,270,000	[3]	$ 2,715,000

[1] Includes $1.6 and $3.7 million in overhead producing credits for 2011 and 2012, respectively, and $1.3 million of proceeds from the sale of oil and gas leases received by the Fund on our behalf during 2011

[2] Includes $2.7 million in purchase price adjustments receivable from the Fund related to natural gas imbalances included with the October 2011 Transferred Properties

[3] Represents a reclamation deposit in escrow as security for abandonment and redemption obligations.