Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net (loss) income	$ (46,581)	$ 28,593
Adjustments to reconcile net income to net cash flows provided by operating activities:
Dry hole costs	51	225
Asset retirement obligations accretion expense	1,354	1,208
Depreciation, depletion and amortization	30,833	24,591
Equity-based compensation cost	4,485	4,280
Impairment of oil and natural gas properties	5,169	635
Noncash derivative activity	38,953	(11,661)
Equity in income of unconsolidated affiliates	(198)
Distribution from unconsolidated affiliates	48
Other	593	2,295
Changes in operating assets and liabilities:
Accounts receivable	(4,527)	(11,150)
Other current assets	(27)	245
Accounts payable and accrued liabilities	11,351	20,382
Other, net	(119)	(1,144)
Net cash flows provided by operating activities	41,385	58,499
Cash flows from investing activities:
Acquisitions of oil and natural gas properties		(36,544)
Final settlement of purchase price of oil and natural gas properties	7,998
Additions to oil and natural gas properties	(21,136)	(29,067)
Proceeds from sale of oil and natural gas properties		5,489
Investments in unconsolidated affiliates	(68,345)	(11,597)
Distributions from unconsolidated affiliates	23
Settlements from acquired derivatives		1,687
Net cash flows used in investing activities	(81,460)	(70,032)
Cash flows from financing activities:
Long-term debt borrowings	85,000	35,000
Repayment of long-term debt borrowings		(460,000)
Proceeds from debt offering		206,000
Loan costs incurred		(3,929)
Proceeds from public equity offering		262,833
Offering costs		(157)
Contributions from general partner	334	5,714
Distributions paid	(33,838)	(29,815)
Net cash flows (used in) provided by financing activities	51,496	15,646
Increase in cash and cash equivalents	11,421	4,113
Cash and cash equivalents - beginning of period	7,486	30,312
Cash and cash equivalents - end of period	$ 18,907	$ 34,425