Consolidated Statement of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income (loss)	$ 194,332	$ 96,429	$ (218,271)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	280,020	248,201	259,639
Write-down of oil and gas properties			508,989
Accretion expense	30,764	34,469	39,306
Deferred income tax provision (benefit)	129,520	50,474	(146,935)
Settlement of asset retirement obligations	(63,391)	(36,901)	(66,780)
Non-cash stock compensation expense	5,905	5,692	5,944
Excess tax benefits	(1,493)	(299)	(2)
Non-cash derivative (income) expense	(2,216)	(324)	5,142
Loss on early extinguishment of debt	607	1,820
Other non-cash expenses	306	1,837	10,971
Change in current income taxes	(19,451)	(10,871)	66,185
(Increase) decrease in accounts receivable	(19,600)	49,633	50,159
(Increase) decrease in other current assets	(66)	74	627
Decrease in inventory	1,619	2,123	17,561
Increase (decrease) in accounts payable	6,039	(773)	(10,200)
Increase (decrease) in other current liabilities	29,583	(18,088)	(14,431)
Other	(1,628)	1,298	(117)
Net cash provided by operating activities	570,850	424,794	507,787
Cash flows from investing activities:
Investment in oil and gas properties	(764,933)	(401,767)	(320,214)
Proceeds from sale of oil and gas properties, net of expenses	87,930	31,635	5,553
Sale of fixed assets			35
Investment in fixed and other assets	(2,247)	(2,949)	(1,412)
Acquisition of non controlling interest in subsidiary		(1,007)	(41)
Net cash used in investing activities	(679,250)	(374,088)	(316,079)
Cash flows from financing activities:
Proceeds from bank borrowings	75,000
Repayments of bank borrowings	(30,000)	(175,000)	(250,000)
Redemption of senior subordinated notes		(200,503)
Proceeds from issuance of senior notes		375,000
Proceeds from stock offering, net of expenses			60,447
Deferred financing costs	(4,017)	(11,474)	(141)
Excess tax benefits	1,493	299	2
Purchase of treasury stock			(347)
Net payments for share based compensation	(2,581)	(1,365)	(513)
Net cash provided by (used in) financing activities	39,895	(13,043)	(190,552)
Net increase (decrease) in cash and cash equivalents	(68,505)	37,663	1,156
Cash and cash equivalents, beginning of year	106,956	69,293	68,137
Cash and cash equivalents, end of year	38,451	106,956	69,293
Cash (paid) refunded during the year for:
Interest, net of amount capitalized	(9,808)	(8,760)	(20,623)
Income taxes	$ 935	$ (26,525)	$ 35,920