Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues:
Oil sales	$ 59,113	$ 108,731	$ 109,409	$ 210,786
Natural gas liquids (NGL) sales	5,729	5,103	9,921	9,069
Natural gas sales	22,959	23,280	50,010	43,163
Total revenues	87,801	137,114	169,340	263,018
Expenses:
Oil and natural gas production	45,220	45,809	94,440	88,343
Production and other taxes	3,986	8,595	8,204	16,550
General and administrative	10,390	14,809	19,259	22,456
Depletion, depreciation, amortization and accretion	36,197	38,537	77,265	72,234
Impairment of long-lived assets	0	2,387	209,402	3,798
Gain (loss) on disposal of assets	(934)	(3,853)	1,007	(1,552)
Total expenses	94,859	106,284	409,577	201,829
Operating income (loss)	(7,058)	30,830	(240,237)	61,189
Other income (expense):
Interest income	176	216	382	439
Interest expense (Notes 2, 6 and 7)	(17,760)	(16,225)	(35,552)	(30,164)
Equity in income of equity method investees	24	191	103	183
Net gains (losses) on commodity derivatives (Notes 6 and 7)	(13,497)	(31,433)	6,983	(47,319)
Other	97	211	702	304
Loss before income taxes	(38,018)	(16,210)	(267,619)	(15,368)
Income tax (expense) benefit	(456)	(278)	291	(592)
Net loss	(38,474)	(16,488)	(267,328)	(15,960)
Distributions to Preferred unitholders	(4,750)	(2,194)	(9,500)	(2,194)
Net loss attributable to unitholders	$ (43,224)	$ (18,682)	$ (276,828)	$ (18,154)
Loss per unit - basic and diluted (Note 9) (in dollars per share)	$ (0.63)	$ (0.33)	$ (4.02)	$ (0.32)
Weighted average number of units used in computing net loss per unit -
Basic (in shares)	68,897	57,372	68,909	57,341
Diluted (in shares)	68,897	57,372	68,909	57,341