CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 40,255	$ 107,031
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	175,497	147,418
Deferred income tax expense	15,081	57,603
(Gain) loss on sale of assets	(138)	1,285
Exploration expense	162	2,040
(Gain) loss on derivative instruments	3,562	0
Amortization of debt issuance costs	1,267	1,126
Stock-based compensation and other	4,490	3,029
Changes in assets and liabilities:
Accounts receivable, net	49,615	(23,418)
Income taxes	8,979	(16,889)
Inventories	(61)	7,076
Other current assets	(192)	1,170
Accounts payable and accrued liabilities	(29,629)	(16,089)
Other assets and liabilities	1,930	39
Stock-based compensation tax benefit	(3,437)	(16,043)
Net cash provided by operating activities	267,381	255,378
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(395,242)	(338,701)
Proceeds from sale of assets	3,081	108
Restricted cash	0	8,382
Investment in equity method investments	(5,078)	(5,937)
Net cash used in investing activities	(397,239)	(336,148)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings from debt	382,000	366,000
Repayments of debt	(257,000)	(291,000)
Dividends paid	(8,263)	(8,332)
Stock-based compensation tax benefit	3,437	16,043
Other	2,678	90
Net cash provided by financing activities	122,852	82,801
Net (decrease) increase in cash and cash equivalents	(7,006)	2,031
Cash and cash equivalents, beginning of period	20,954	23,400
Cash and cash equivalents, end of period	$ 13,948	$ 25,431