Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income	$ 37,710	$ 50,245
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, depletion and amortization	91,857	75,386
Deferred income taxes	22,007	28,302
Gain from oil hedging activities	(19,512)	(24,309)
Non-hedge derivative gains	(17,346)	(62,065)
Loss on extinguishment of debt	0	21,696
(Gain) loss on sale of assets	(224)	48
Other	1,387	1,461
Change in assets and liabilities
Accounts receivable	(15,245)	(9,023)
Inventories	(1,568)	(6,144)
Prepaid expenses and other assets	2,480	2,676
Accounts payable and accrued liabilities	(5,912)	675
Revenue distribution payable	4,023	(3,728)
Stock-based compensation	342	1,076
Net cash provided by operating activities	99,999	76,296
Cash flows from investing activities
Purchase of property and equipment and oil and natural gas properties	(248,206)	(237,144)
Proceeds from dispositions of property and equipment and oil and natural gas properties	68,133	39,696
Settlement of non-hedge derivative instruments	15,918	13,604
Other	(664)	22
Net cash used in investing activities	(164,819)	(183,822)
Cash flows from financing activities
Proceeds from long-term debt	100,650	72,822
Repayment of long-term debt and capital lease obligations	(33,623)	(36,746)
Proceeds from Senior Notes	0	400,000
Repayment of Senior Notes	0	(325,000)
Payment of debt issuance costs and other financing fees	0	(8,867)
Payment of debt extinguishment costs	0	(15,809)
Net cash provided by financing activities	67,027	86,400
Net increase (decrease) in cash and cash equivalents	2,207	(21,126)
Cash and cash equivalents at beginning of period	29,819	34,589
Cash and cash equivalents at end of period	$ 32,026	$ 13,463