CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 115,882	$ 105,180
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	255,497	260,982
Accretion expense	25,012	24,926
Deferred income tax provision	77,001	59,573
Settlement of asset retirement obligations	(61,178)	(47,211)
Non-cash stock compensation expense	7,583	6,800
Excess tax benefits	(156)	(882)
Non-cash derivative expense (income)	1,626	(584)
Non-cash interest expense	12,384	9,068
Other non-cash expense		16
Change in current income taxes	(704)	(3,240)
Increase in accounts receivable	(22,277)	(15,832)
(Increase) decrease in other current assets	2,187	(2,456)
Decrease in inventory	158	136
Increase in accounts payable	8,035	6,116
Increase (decrease) in other current liabilities	20,251	(24,301)
Other	(1,791)	(4,378)
Net cash provided by (used in) operating activities	439,510	373,913
Cash flows from investing activities:
Investment in oil and gas properties	(472,304)	(445,311)
Proceeds from sale of oil and gas properties, net of expenses	6,300	403
Sale of fixed assets		134
Investment in fixed and other assets	(3,830)	(3,998)
Change in restricted funds	(2,394)
Net cash used in investing activities	(472,228)	(448,772)
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	156	882
Net payments for share-based compensation	(3,733)	(3,773)
Net cash (used in) provided by financing activities	(3,588)	212,594
Effect of exchange rate changes on cash	(145)
Net change in cash and cash equivalents	(36,451)	137,735
Cash and cash equivalents, beginning of period	279,526	38,451
Cash and cash equivalents, end of period	$ 243,075	$ 176,186