Condensed Consolidated Statement of Cash Flows (Unaudited) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income	$ 96,988	$ 53,290
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	140,315	124,418
Accretion expense	15,434	16,924
Deferred income tax provision	57,664	34,393
Settlement of asset retirement obligations	(33,568)	(19,798)
Non-cash stock compensation expense	3,138	2,741
Excess tax benefits	(1,060)	(294)
Non-cash derivative (income)	(118)	(1,818)
Loss on early extinguishment of debt	607	1,820
Other non-cash (income) expense	(155)	519
Change in current income taxes	(6,245)	(8,813)
(Increase) decrease in accounts receivable	(37,428)	27,500
(Increase) in other current assets	(476)	(153)
Decrease in inventory	1,163	936
Increase (decrease) in accounts payable	5,854	(15)
Increase (decrease) in other current liabilities	4,440	(21,469)
Other	(21)	153
Net cash provided by operating activities	246,532	210,334
Cash flows from investing activities:
Investment in oil and gas properties	(272,451)	(169,983)
Proceeds from sale of oil and gas properties, net of expenses	6,692	29,727
Investment in fixed and other assets	(894)	(1,125)
Net cash used in investing activities	(266,653)	(141,381)
Cash flows from financing activities:
Repayments of bank borrowings	0	(125,000)
Redemption of senior subordinated notes	0	(200,503)
Proceeds from issuance of senior notes	0	275,000
Deferred financing costs	(4,017)	(9,701)
Excess tax benefits	1,060	294
Net payments for share based compensation	(1,857)	(1,071)
Net cash used in financing activities	(4,814)	(60,981)
Net increase (decrease) in cash and cash equivalents	(24,935)	7,972
Cash and cash equivalents, beginning of period	106,956	69,293
Cash and cash equivalents, end of period	$ 82,021	$ 77,265