Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net loss	$ (26,041)	$ (6,470)
Adjustments to reconcile net loss to net cash flows provided by operating activities:
Asset retirement obligations accretion expense	3,744	3,763
Depreciation, depletion and amortization	86,439	81,127
Equity-based compensation cost	13,080	12,390
Impairment of oil and natural gas properties	8,141	17,752
Noncash derivative activity	26,162	39,395
Equity in (income) losses of unconsolidated affiliates	(237)	60
Distribution from unconsolidated affiliates	171
Other	2,313	4,698
Changes in operating assets and liabilities:
Accounts receivable	(6,430)	3,138
Other current assets	(5,435)	656
Accounts payable and accrued liabilities	17,889	20,479
Other, net	(561)	(1,955)
Net cash flows provided by operating activities	119,235	175,033
Cash flows from investing activities:
Acquisitions of oil and natural gas properties		(118,925)
Final settlement of purchase price of oil and natural gas properties	7,998
Additions to oil and natural gas properties	(75,799)	(100,392)
Proceeds from sale of oil and natural gas properties		5,522
Investments in unconsolidated affiliates	(172,003)	(18,998)
Distributions from unconsolidated affiliates	33
Settlements from acquired derivatives		4,166
Net cash flows used in investing activities	(239,771)	(228,627)
Cash flows from financing activities:
Long-term debt borrowings	225,000	120,000
Repayment of long-term debt borrowings		(460,000)
Proceeds from debt offering		206,000
Loan costs incurred		(4,152)
Proceeds from public equity offering		262,833
Offering costs		(304)
Contributions from general partner	334	5,714
Distributions paid	(101,646)	(95,845)
Net cash flows provided by financing activities	123,688	34,246
Increase (decrease) in cash and cash equivalents	3,152	(19,348)
Cash and cash equivalents - beginning of period	7,486	30,312
Cash and cash equivalents - end of period	$ 10,638	$ 10,964