Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash	$ 19,666	$ 31,836
Accounts receivable	52,296	41,897
Due from general partner	7	165
Derivative instruments	40,809	45,522
Prepaid and other current assets	2,533	2,642
Total current assets	115,311	122,062
Noncurrent assets:
Evaluated	1,718,308	1,656,146
Unevaluated	4,860	11,500
Gross oil and natural gas properties	1,723,168	1,667,646
Less accumulated depreciation, depletion and amortization	(260,854)	(203,377)
Total property and equipment, net	1,462,314	1,464,269
Derivative instruments	90,499	76,621
Other assets	27,795	23,575
Total noncurrent assets	1,580,608	1,564,465
Total assets	1,695,919	1,686,527
Current liabilities:
Due to affiliates	1,214
Current portion of asset retirement obligations	1,562	1,426
Derivative instruments	8,248	8,727
Accrued and other liabilities	64,516	46,284
Total current liabilities	75,540	56,437
Noncurrent liabilities:
Long-term debt	776,334	766,076
Derivative instruments	6,829	16,993
Asset retirement obligations	128,575	125,565
Other liabilities	6,615	6,892
Total noncurrent liabilities	918,353	915,526
Commitments and contingencies (See Note 9)
Partners' capital:
Class C convertible preferred unitholders (16,666,667 issued and outstanding as June 30, 2013 and December 31, 2012)	380,765	373,068
General partner (51,036 units issued and outstanding as of June 30, 2013 and December 31, 2012)	683	710
Class B convertible unitholders (6,133,558 and zero units issued and outstanding as of June 30, 2013 and December 31, 2012)
Total partners' capital	702,026	714,564
Total liabilities and partners' capital	1,695,919	1,686,527
Limited Partners-Public Common [Member]
Partners' capital:
Limited partners' capital account	386,442	403,757
Total partners' capital	386,442	403,757
Limited Partners-Affiliated - Common [Member]
Partners' capital:
Limited partners' capital account	(65,864)	(62,971)
Total partners' capital	$ (65,864)	$ (62,971)