Condensed Consolidated Balance Sheets (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 26,392	$ 23,127
Accounts receivable:
Oil, natural gas and natural gas liquids revenues	36,600	27,742
Related party	3,967
Other	300	441
Derivative asset	51,215	55,100
Assets held for sale	11,402
Other current assets	1,047	1,158
Total current assets	130,923	107,568
Oil and natural gas properties, net of accumulated depreciation, depletion and amortization; June 30, 2011, $210,073; December 31, 2010, $176,897	1,300,294	1,324,240
Other property, net of accumulated depreciation and amortization; June 30, 2011, $536; December 31, 2010, $465	1,495	1,567
Long-term derivative asset	26,576	51,497
Other assets	7,533	1,885
Total assets	1,466,821	1,486,757
Accounts payable and accrued liabilities:
Third party	27,642	20,678
Related party		182
Liabilities related to assets held for sale	2,895
Derivative liability	1,178	1,943
Total current liabilities	31,715	22,803
Asset retirement obligations	68,266	67,175
Long-term debt	480,183	619,000
Long-term liabilities	988	3,048
Long-term derivative liability	6,594	784
Commitments and contingencies
Owners' equity:
Common unitholders - 34,173,650 units and 30,510,313 units issued and outstanding as of June 30, 2011 and December 31, 2010, respectively	887,843	779,327
General partner interest	(8,768)	(5,380)
Total owners' equity	879,075	773,947
Total liabilities and owners' equity	$ 1,466,821	$ 1,486,757