Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 10,638	$ 7,486
Accounts receivable:
Oil, natural gas and natural gas liquids revenues	38,278	34,909
Related party	7,562	1,422
Other	214	11,263
Derivative asset	22,807	40,771
Other current assets	7,185	1,750
Total current assets	86,684	97,601
Oil and natural gas properties, net of accumulated depreciation, depletion and amortization; September 30, 2013, $475,543; December 31, 2012, $389,206	1,853,014	1,875,890
Other property, net of accumulated depreciation and amortization; September 30, 2013, $714; December 31, 2012, $598	1,266	1,325
Long-term derivative asset	37,680	45,839
Investments in unconsolidated affiliates	206,581	34,545
Other assets	8,465	10,214
Total assets	2,193,690	2,065,414
LIABILITIES AND OWNERS' EQUITY
Accounts payable and accrued expenses	60,745	40,171
Derivative liability	39
Total current liabilities	60,784	40,171
Asset retirement obligations	99,307	102,707
Long-term debt	1,084,276	859,218
Other long-term liabilities	1,589	3,494
Commitments and contingencies
Owners' equity:
Common unitholders - 42,599,080 units and 42,320,707 units issued and outstanding as of September 30, 2013 and December 31, 2012, respectively	962,017	1,072,175
General partner interest	(14,283)	(12,351)
Total owners' equity	947,734	1,059,824
Total liabilities and owners' equity	$ 2,193,690	$ 2,065,414