Organization And Operations (Schedule Of Net Assets Contributed By The Fund - December 2012) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 28, 2012		Dec. 31, 2011	Oct. 03, 2011
Organization And Operations [Abstract]
Evaluated	$ 1,656,146	$ 141,315		$ 1,076,828
Accumulated depreciation, depletion and amortization		(45,416)
Other assets		10,732	[1]
Derivative instrument asset, net		(2,948)			64,671
Long-term debt		(115,000)
Asset retirement obligation		(34,261)			(26,294)
Net assets acquired		(45,578)			249,331
Purchase price adjustments		5,270	[2]		2,715
Net assets contributed by Predecessor's		$ (40,308)	[1]		$ 252,046	[3]

[1] The net assets contributed to us include the historical book value of the Predecessor as prescribed by our accounting policy for transactions between entities under common control in Note 2 - Summary of Significant Accounting Policies and a $5.3 million purchase price adjustment related to novated derivatives unwound by the Partnership.

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

[3] The net assets contributed to us include the historical book value of the Predecessor as prescribed by our accounting policy for transactions between entities under common control in Note 2 - Summary of Significant Accounting Policies and a $2.7 million purchase price adjustment for natural gas imbalances in accordance with the purchase and sale agreement.