CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Current assets
Cash and cash equivalents	$ 69,768	$ 236,001
Accounts receivable - trade, net	264,279	184,624
Derivative instruments	141,143	234,675
Other current assets	56,757	55,609
Total current assets	531,947	710,909
Noncurrent assets
Oil and natural gas properties (successful efforts method)	6,740,667	5,664,503
Less accumulated depletion and amortization	(855,314)	(719,035)
Oil and natural gas properties, successful efforts method, net	5,885,353	4,945,468
Other property and equipment	164,120	139,903
Less accumulated depreciation	(41,033)	(35,151)
Other property and equipment, net	123,087	104,752
Derivative instruments	29,473	56,895
Other noncurrent assets	112,955	115,124
Noncurrent assets, excluding property, total	142,428	172,019
Total noncurrent assets	6,150,868	5,222,239
Total assets	6,682,815	5,933,148
Current liabilities
Accounts payable and accrued expenses	305,014	219,830
Derivative instruments	8,750	12,839
Other accrued liabilities	67,674	82,439
Total current liabilities	381,438	315,108
Noncurrent liabilities
Senior notes, net	3,052,888	2,742,902
Derivative instruments	191,405	39,797
Other noncurrent liabilities	57,886	47,125
Total noncurrent liabilities	3,302,179	2,829,824
Commitments and contingencies (Note 10)
Unitholders' capital
176,980,978 units and 159,009,795 units issued and outstanding at June 30, 2011, and December 31, 2010, respectively	2,969,654	2,549,099
Accumulated income	29,544	239,117
Total unitholders' capital	2,999,198	2,788,216
Total liabilities and unitholders' capital	$ 6,682,815	$ 5,933,148