Consolidated Statement of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income (loss)	$ 251	$ 202
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	465	339
Deferred tax provision (benefit)	54	88
Stock-based compensation	17	14
Commodity derivative (income) expense	(159)	13
Cash receipts on derivative settlements, net	86	95
Other non-cash charges	3	3
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(5)	(6)
(Increase) decrease in inventories	(12)	(26)
(Increase) decrease in other current assets	(20)	(19)
(Increase) decrease in other assets	(1)	(4)
Increase (decrease) in accounts payable and accrued liabilities	(76)	29
Increase (decrease) in advances from joint owners	(26)	4
Increase (decrease) in other liabilities	(2)	(3)
Net cash provided by operating activities	575	729
Cash flows from investing activities:
Additions to oil and gas properties	(875)	(1,077)
Acquisitions of oil and gas properties	(9)	(311)
Proceeds from sales of oil and gas properties	329	130
Additions to furniture, fixtures and equipment	(13)	(10)
Redemptions of investments	0	1
Net cash used in investing activities	(568)	(1,267)
Cash flows from financing activities:
Proceeds from borrowings under credit arrangements	1,663	2,371
Repayments of borrowings under credit arrangements	(1,749)	(1,786)
Proceeds from issuance of Senior Notes	1,000	0
Debt issue costs	(10)	(8)
Repayment of senior subordinated notes	(325)	0
Proceeds from issuances of common stock	0	11
Purchases of treasury stock, net	(6)	(15)
Net cash provided by (used in) financing activities	573	573
Increase (decrease) in cash and cash equivalents	580	35
Cash and cash equivalents, beginning of period	76	39
Cash and cash equivalents, end of period	$ 656	$ 74