CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010
OPERATING ACTIVITIES
Net income	$ 580,516		$ 421,180
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, depletion and amortization	548,156		580,892
Amortization of deferred major repair costs	23,520		16,150
Expenditures for asset retirements	(16,441)		(25,280)
Dry hole costs	105,307		29,841
Amortization of undeveloped leases	60,530		48,378
Accretion of asset retirement obligations	19,145		15,457
Deferred and noncurrent income tax charges	6,220		33,233
Pretax gain from disposition of assets	(23,132)		(789)
Net decrease (increase) in noncash operating working capital	(455,655)		249,780
Other operating activities, net	69,776		78,901
Net cash provided by operating activities	917,942		1,447,743
INVESTING ACTIVITIES
Property additions and dry hole costs	(1,258,731)		(992,256)
Proceeds from sales of assets	27,538		1,792
Purchase of investment securities	(675,606)	[1]	(1,263,026)	[1]
Proceeds from maturity of investment securities	754,082	[1]	1,239,290	[1]
Expenditures for major repairs	(680)		(89,102)
Other - net	6,753		(23,110)
Net cash required by investing activities	(1,146,644)		(1,126,412)
FINANCING ACTIVITIES
Borrowings (repayments) of notes payable	594,980		(122,019)
Repayment of nonrecourse debt of a subsidiary	0		(2,269)
Proceeds from exercise of stock options and employee stock purchase plans	7,900		14,798
Excess tax benefits related to exercise of stock options	4,068		483
Withholding tax on stock-based incentive awards	(8,014)		(5,170)
Issue cost of debt facility	(7,672)		0
Cash dividends paid	(106,312)		(95,700)
Net cash provided (required) by financing activities	484,950		(209,877)
Effect of exchange rate changes on cash and cash equivalents	9,173		(13,778)
Net increase in cash and cash equivalents	265,421		97,676
Cash and cash equivalents, beginning	535,825		301,144
Cash and cash equivalents, ending	$ 801,246		$ 398,820

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