CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities
Net income (loss)	$ (104,589)	$ (132,915)	$ 19,667
Adjustments to reconcile net income (loss) to net cash provided by operating activities from continuing operations:
Income from discontinued operations	0	0	(36,832)
Gain on sale of discontinued operations	0	0	(86,662)
Non-cash portion of loss on extinguishment of debt	3,144	22,456	0
Loss on firm transportation commitment	17,332	0	0
Depreciation, depletion and amortization	206,336	162,534	134,700
Impairments	104,484	104,688	45,959
Derivative contracts:
Net gains	(36,187)	(15,651)	(41,906)
Cash settlements	29,723	27,380	32,818
Deferred income taxes (benefit)	(68,676)	(85,501)	42,528
(Gain) loss on sales of assets, net	(4,282)	(2,474)	61
Non-cash exploration expense	32,634	60,940	36,275
Non-cash interest expense	4,062	6,807	11,984
Share-based compensation (equity-classified)	6,347	7,430	7,811
Other, net	1,004	275	(209)
Changes in operating assets and liabilities:
Accounts receivable, net	9,907	(1,792)	(19,964)
Income taxes receivable and payable, net	31,439	(2,815)	2,627
Accounts payable and accrued expenses	9,710	(6,552)	10,877
Other assets and liabilities	(930)	(69)	(79,895)
Net cash provided by operating activities from continuing operations	241,458	144,741	79,839
Cash flows from investing activities
Capital expenditures - property and equipment	(370,907)	(445,623)	(405,994)
Proceeds from the sale of PVG units, net (Note 3)	0	0	139,120
Proceeds from sales of assets, net	96,719	39,368	25,567
Other, net	180	100	1,192
Net cash used in investing activities for continuing operations	(274,008)	(406,155)	(240,115)
Cash flows from financing activities
Proceeds from the issuance of preferred stock, net	110,337	0	0
Proceeds from the issuance of common stock, net	43,474	0	0
Proceeds from the issuance of senior notes	0	300,000	0
Retirement of convertible notes	(4,915)	(232,963)	0
Proceeds from revolving credit facility borrowings	211,000	114,000	0
Repayment of revolving credit facility borrowings	(310,000)	(15,000)	0
Debt issuance costs paid	(2,032)	(8,854)	0
Dividends paid	(5,176)	(10,316)	(10,271)
Proceeds from the sale of PVG units, net (Note 3)	0	0	199,125
Distributions received from discontinued operations	0	0	11,218
Other, net	0	1,148	2,098
Net cash provided by financing activities from continuing operations	42,688	148,015	202,170
Cash flows from discontinued operations
Net cash provided by operating activities	0	0	77,759
Net cash used in investing activities	0	0	(18,112)
Net cash used in provided by financing activities	0	0	(59,647)
Net cash provided by discontinued operations	0	0	0
Net increase (decrease) in cash and cash equivalents	10,138	(113,399)	41,894
Cash and cash equivalents - beginning of period	7,512	120,911	79,017
Cash and cash equivalents - end of period	17,650	7,512	120,911
Cash paid for:
Interest (net of amounts capitalized)	54,808	44,589	43,531
Income taxes (net of refunds received)	$ (32,603)	$ 210	$ 28,184