CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 34,793	$ 30,638
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	49,086	51,049
Impairment of property and equipment	4,424	11,114
Exploration costs	1,051	5,769
(Gain) loss on sales of assets and impairment of inventory, net	(14,218)	1,044
Deferred income tax expense	19,149	16,863
Non-cash employee compensation	4,963	5,079
Unrealized (gain) loss on derivatives	9,069	(25,871)
Accretion of abandonment obligations	1,371	1,294
Amortization of debt issue costs	1,130	774
Loss on early extinguishment of long-term debt	4,594
Changes in operating working capital:
Accounts receivable	2,067	5,234
Accounts payable	974	(3,403)
Other	1,271	(2,907)
Net cash provided by operating activities	119,724	96,677
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to property and equipment	(180,281)	(135,528)
Proceeds from sales of assets	12,105	73,011
Change in equipment inventory	4,783	1,300
Other	(110)	(98)
Net cash used in investing activities	(163,503)	(61,315)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	341,855
Repayments of long-term debt	(286,165)	(39,000)
Premium on early extinguishment of long-term debt	(2,765)
Proceeds from exercise of stock options	213
Net cash provided by (used in) financing activities	53,138	(39,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	9,359	(3,638)
CASH AND CASH EQUIVALENTS
Beginning of period	8,720	14,013
End of period	18,079	10,375
SUPPLEMENTAL DISCLOSURES
Cash paid for interest, net of amounts capitalized	$ 1,754	$ 11,735