CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Operating Activities
Net income	$ 970,876		$ 872,702	[1]	$ 798,081	[1]
Adjustments to reconcile net income to net cash provided by operating activities
Income from discontinued operations	(6,830)		(143,231)	[1]	(49,001)	[1]
Depreciation, depletion and amortization	1,375,577		1,079,750	[1]	1,092,107	[1]
Impairment of long-lived assets	260,988		368,600	[1]	0	[1]
Amortization of deferred major repair costs	22,818		23,076	[1]	15,561	[1]
Expenditures for asset retirements	(40,434)		(21,490)	[1]	(36,496)	[1]
Dry hole costs	181,924		250,954	[1]	74,891	[1]
Amortization of undeveloped leases	129,750		118,211	[1]	108,026	[1]
Accretion of asset retirement obligations	39,341		34,724	[1]	29,580	[1]
Deferred and noncurrent income tax charges	316,587		156,983	[1]	146,583	[1]
Pretax (gains) losses from disposition of assets	1,258		(22,679)	[1]	(884)	[1]
Net decrease (increase) in noncash operating working capital	(401,103)		(825,705)	[1]	639,612	[1]
Other operating activities - net	144,388		67,955	[1]	151,012	[1]
Net cash provided by continuing operations	2,995,140		1,959,850	[1]	2,969,072	[1]
Net cash provided by discontinued operations	61,141		185,535	[1]	159,486	[1]
Net cash provided by operating activities	3,056,281		2,145,385	[1]	3,128,558	[1]
Investing Activities
Property additions and dry hole costs	(3,674,621)		(2,603,158)	[1]	(2,188,517)	[1]
Acquisition of ethanol plant	0		0	[1]	(40,000)	[1]
Proceeds from sale of property, plant and equipment	569		27,776	[1]	2,189	[1]
Expenditures for major repairs	(12,790)		(5,409)	[1]	(61,387)	[1]
Purchase of investment securities	(1,619,308)	[2]	(1,689,087)	[1],[2]	(2,388,720)	[1],[2]
Proceeds from maturity of investment securities	2,035,798	[2]	1,773,552	[1],[2]	2,551,187	[1],[2]
Other investing activities - net	11,086		8,014	[1]	(38,157)	[1]
Investing activities of discontinued operations
Sales proceeds	0		950,010	[1]	0	[1]
Other	(58,156)		(76,052)	[1]	(165,407)	[1]
Net cash required by investing activities	(3,317,422)		(1,614,354)	[1]	(2,328,812)	[1]
Financing Activities
Additions to long-term debt	1,995,467		0	[1]	0	[1]
Repayments of debt	(350,000)		(340,041)	[1]	(332,038)	[1]
Repayment of nonrecourse debt of a subsidiary	0		0	[1]	(82,000)	[1]
Purchase of treasury stock	(250,000)		0	[1]	0	[1]
Proceeds from exercise of stock options and employee stock purchase plans	12,324		15,551	[1]	42,995	[1]
Excess tax benefits related to exercise of stock options	2,647		4,838	[1]	11,672	[1]
Withholding tax on stock-based incentive awards	(3,341)		(8,014)	[1]	(5,170)	[1]
Issue cost of debt facility	(6,959)		(7,905)	[1]	0	[1]
Cash dividends paid	(714,429)		(212,752)	[1]	(201,405)	[1]
Net cash provided (required) by financing activities	685,709		(548,323)	[1]	(565,946)	[1]
Effect of exchange rate changes on cash and cash equivalents	8,875		(4,660)	[1]	881	[1]
Net increase (decrease) in cash and cash equivalents	433,443		(21,952)	[1]	234,681	[1]
Cash and cash equivalents, beginning	513,873	[1]	535,825	[1]	301,144	[1]
Cash and cash equivalents, ending	$ 947,316		$ 513,873	[1]	$ 535,825	[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.