Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash	$ 3,661	$ 725
Accounts receivable, net:
Oil and natural gas	41,235	49,390
Joint interest owners	12,424	16,235
Other	254	237
Fair value of derivatives (Notes 6 and 7)	63,951	120,305
Prepaid expenses and other current assets	5,708	5,362
Total current assets	127,233	192,254
Oil and natural gas properties using the successful efforts method, at cost:
Proved properties	2,976,550	2,946,820
Unproved properties	48,322	47,613
Accumulated depletion, depreciation, amortization and impairment	(1,626,689)	(1,354,459)
Oil and natural gas properties using the successful efforts method, at cost	1,398,183	1,639,974
Other property and equipment, net of accumulated depreciation and amortization of $8,126 and $7,446, respectively	3,269	3,767
Operating rights, net of amortization of $4,731 and $4,509, respectively	2,286	2,508
Fair value of derivatives (Notes 6 and 7)	18,605	32,794
Other assets, net of amortization of $13,996 and $12,551, respectively	24,179	24,255
Investments in equity method investees	624	3,054
Total assets	1,574,379	1,898,606
Current liabilities:
Accounts payable	1,416	2,787
Accrued oil and natural gas liabilities (Note 1)	54,667	78,615
Fair value of derivatives (Notes 6 and 7)	985	2,080
Asset retirement obligation (Note 8)	3,028	3,028
Other (Notes 2 and 10)	9,757	11,066
Total current liabilities	69,853	97,576
Long-term debt (Note 2)	966,111	938,876
Asset retirement obligation (Note 8)	241,611	223,497
Other long-term liabilities	1,294	1,452
Total liabilities	$ 1,278,869	$ 1,261,401
Commitments and contingencies (Note 5)
Partners' equity (Note 9):
Limited partners' equity - 57,405,398 and 57,280,049 units issued and outstanding at June 30, 2014 and December 31, 2013	$ 35,261	$ 376,885
General partner's equity (approximately 0.03%)	(18)	53
Total partners' equity	295,510	637,205
Total liabilities and partners' equity	1,574,379	1,898,606
Incentive distribution equity - 100,000 units issued and outstanding at June 30, 2015 and December 31, 2014
Partners' equity (Note 9):
Incentive distribution equity - 100,000 units issued and outstanding at June 30, 2015 and December 31, 2014	30,814	30,814
Series A Preferred equity - 2,300,000 units issued and outstanding at June 30, 2015 and December 31, 2014
Partners' equity (Note 9):
Preferred equity	55,192	55,192
Series B Preferred equity - 7,200,000 units issued and outstanding at June 30, 2015 and December 31, 2014
Partners' equity (Note 9):
Preferred equity	$ 174,261	$ 174,261