Condensed Consolidated Statement of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 81,521	$ 96,988
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	171,708	140,315
Accretion expense	16,521	15,434
Deferred income tax provision	46,474	57,664
Settlement of asset retirement obligations	(21,918)	(33,568)
Non-cash stock compensation expense	4,271	3,138
Excess tax benefits	(795)	(1,060)
Non-cash derivative income	(2,758)	(118)
Loss on early extinguishment of debt		607
Non-cash interest expense	5,278	959
Change in current income taxes	(3,921)	(6,245)
Increase in accounts receivable	(37,517)	(37,428)
Increase in other current assets	(124)	(476)
Decrease in inventory	36	1,163
Increase in accounts payable	8,413	5,854
Increase (decrease) in other current liabilities	(17,304)	4,440
Other	(465)	(1,135)
Net cash provided by operating activities	249,420	246,532
Cash flows from investing activities:
Investment in oil and gas properties	(275,813)	(272,451)
Proceeds from sale of oil and gas properties, net of expenses	403	6,692
Sale of fixed assets	149
Investment in fixed and other assets	(1,900)	(894)
Net cash used in investing activities	(277,161)	(266,653)
Cash flows from financing activities:
Proceeds from bank borrowings	25,000
Repayments of bank borrowings	(70,000)
Proceeds from issuance of senior convertible notes	300,000
Financing costs of senior convertible notes	(8,855)
Proceeds from Sold Warrants	40,170
Payments for Purchased Call Options	(70,830)
Deferred financing costs		(4,017)
Excess tax benefits	795	1,060
Net payments for share based compensation	(3,141)	(1,857)
Net cash provided by (used in) financing activities	213,139	(4,814)
Net change in cash and cash equivalents	185,398	(24,935)
Cash and cash equivalents, beginning of period	38,451	106,956
Cash and cash equivalents, end of period	$ 223,849	$ 82,021