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	$ 35,103	$ 93,823	$ 36,938
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	142,687	104,880	101,145
Impairment of property and equipment	5,944	10,355	11,908
Exploration costs	4,222	20,840	9,074
(Gain) loss on sales of assets and impairment of inventory, net	(463)	(14,078)	(1,930)
Deferred income tax expense	22,008	52,550	20,259
Non-cash employee compensation	(404)	12,866	13,898
Unrealized (gain) loss on derivatives	(17,858)	(4,506)	9,153
Amortization of debt issue costs and original issue discount	2,554	2,342	1,648
Accretion of asset retirement obligations	3,696	2,757	2,623
Loss on early extinguishment of long-term debt	0	5,501	0
Amortization of deferred revenue from volumetric production payment	(8,295)	0	0
Changes in operating working capital:
Accounts receivable	7,299	(10,739)	(10,036)
Accounts payable	(9,386)	7,551	19,144
Other	2,115	(4,095)	(5,573)
Net cash provided by operating activities	189,222	280,047	208,251
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to property and equipment	(526,521)	(413,013)	(285,655)
Proceeds from volumetric production payment	45,479	0	0
Proceeds from sales of assets	3,778	13,902	77,216
(Increase) decrease in equipment inventory	1,313	(5,305)	4,638
Other	(82)	(497)	18
Net cash used in investing activities	(476,033)	(404,913)	(203,783)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	280,000	547,710	0
Repayments of long-term debt	0	(411,500)	(10,000)
Premium on early extinguishment of long-term debt	0	(2,765)	0
Proceeds from exercise of stock options	12	226	239
Net cash provided by (Used in) financing activities	280,012	133,671	(9,761)
NET INCREASE IN CASH AND CASH EQUIVALENTS	(6,799)	8,805	(5,293)
CASH AND CASH EQUIVALENTS
Beginning of period	17,525	8,720	14,013
End of period	10,726	17,525	8,720
SUPPLEMENTAL DISCLOSURES
Cash paid for interest, net of amounts capitalized	35,932	23,923	22,457
Cash paid for income taxes	$ 0	$ 0	$ 0