CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 79,780	$ 81,521
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	162,644	171,708
Accretion expense	16,581	16,521
Deferred income tax provision	56,422	46,474
Settlement of asset retirement obligations	(37,335)	(21,918)
Non-cash stock compensation expense	4,866	4,271
Excess tax benefits	(104)	(795)
Non-cash derivative (income) expense	311	(2,758)
Non-cash interest expense	8,181	5,278
Change in current income taxes	(16,399)	(3,921)
(Increase) decrease in accounts receivable	1,138	(37,517)
Increase in other current assets	(245)	(124)
Decrease in inventory	158	36
Increase in accounts payable	6,593	8,413
Decrease in other current liabilities	(3,170)	(17,304)
Other	(3,448)	(465)
Net cash provided by (used in) operating activities	275,973	249,420
Cash flows from investing activities:
Investment in oil and gas properties	(320,218)	(275,813)
Proceeds from sale of oil and gas properties, net of expenses		403
Sale of fixed assets		149
Investment in fixed and other assets	(1,711)	(1,900)
Change in restricted funds	(3,515)
Net cash used in investing activities	(325,444)	(277,161)
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
Deferred financing costs of senior convertible notes		(8,855)
Proceeds from sold warrants		40,170
Payments for purchased call options		(70,830)
Deferred financing costs	(11)
Excess tax benefits	104	795
Net payments for share based compensation	(3,590)	(3,141)
Net cash (used in) provided by financing activities	(3,497)	213,139
Effect of exchange rate changes on cash	(186)
Net change in cash and cash equivalents	(53,154)	185,398
Cash and cash equivalents, beginning of period	279,526	38,451
Cash and cash equivalents, end of period	$ 226,372	$ 223,849