CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
OPERATING ACTIVITIES
Net income	$ 812,189		$ 986,630	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Income from discontinued operations	(10,534)		(139,206)	[1]
Depreciation, depletion and amortization	972,663		783,531	[1]
Amortization of deferred major repair costs	16,876		17,357	[1]
Expenditures for asset retirements	(22,949)		(15,171)	[1]
Dry hole costs	89,645		118,585	[1]
Amortization of undeveloped leases	107,151		90,623	[1]
Accretion of asset retirement obligations	29,052		26,162	[1]
Deferred and noncurrent income tax charges	155,616		110,670	[1]
Pretax gain from disposition of assets	(94)		(23,192)	[1]
Net increase in noncash operating working capital	(217,240)		(305,221)	[1]
Other operating activities, net	120,862		36,121	[1]
Net cash provided by continuing operations	2,053,237		1,686,889	[1]
Net cash provided by discontinued operations	47,990		189,858	[1]
Net cash provided by operating activities	2,101,227		1,876,747	[1]
INVESTING ACTIVITIES
Property additions and dry hole costs	(2,232,067)		(1,845,000)	[1]
Proceeds from sales of assets	388		27,629	[1]
Purchase of investment securities	(1,360,746)	[2]	(1,233,321)	[1],[2]
Proceeds from maturity of investment securities	1,401,235	[2]	1,356,175	[1],[2]
Expenditures for major repairs	(11,367)		(2,826)	[1]
Investing activities of discontinued operations:
Sales proceeds	0		403,833	[1]
Other	(36,524)		(58,534)	[1]
Other - net	8,898		7,150	[1]
Net cash required by investing activities	(2,230,183)		(1,344,894)	[1]
FINANCING ACTIVITIES
Borrowings of notes payable	934,899		384,970	[1]
Maturities of notes payable	(350,000)		0	[1]
Proceeds from exercise of stock options and employee stock purchase plans	11,138		8,245	[1]
Excess tax benefits related to exercise of stock options	1,957		4,119	[1]
Withholding tax on stock-based incentive awards	(3,522)		(8,014)	[1]
Issue cost of notes payable and debt facility	(4,285)		(8,619)	[1]
Cash dividends paid	(167,520)		(159,529)	[1]
Net cash provided by financing activities	422,667		221,172	[1]
Effect of exchange rate changes on cash and cash equivalents	9,110		(9,869)	[1]
Net increase in cash and cash equivalents	302,821		743,156	[1]
Cash and cash equivalents, beginning	513,873		535,825	[1]
Cash and cash equivalents, ending	$ 816,694		$ 1,278,981	[1]

[1] Reclassified to conform to current presentation.

[2] Investments are Canadian government securities with maturities greater than 90 days at the date of acquisition.