Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities
Net Income	$ 570,279	$ 1,091,123	$ 160,654
Items Not Requiring (Providing) Cash
Depreciation, Depletion and Amortization	3,169,703	2,516,381	1,941,926
Impairments	1,270,735	1,031,037	742,647
Stock-Based Compensation Expenses	127,778	128,345	107,378
Deferred Income Taxes	292,938	499,300	76,245
Gains on Asset Dispositions, Net	(192,660)	(492,909)	(223,538)
Other, Net	672	15,139	(468)
Dry Hole Costs	14,970	53,230	72,486
Mark-to-Market Commodity Derivative Contracts
Total Gains	(393,744)	(626,053)	(61,912)
Realized Gains	711,479	180,701	7,033
Excess Tax Benefits from Stock-Based Compensation	(67,035)	0	0
Other, Net	14,411	26,454	17,273
Changes in Components of Working Capital and Other Assets and Liabilities
Accounts Receivable	(178,683)	(339,780)	(339,126)
Inventories	(156,762)	(176,623)	(171,791)
Accounts Payable	(17,150)	351,087	654,688
Accrued Taxes Payable	78,094	92,589	(53,098)
Other Assets	(118,520)	(23,625)	(32,169)
Other Liabilities	36,114	14,986	19,342
Changes in Components of Working Capital Associated with Investing and Financing Activities	74,158	237,028	(208,968)
Net Cash Provided by Operating Activities	5,236,777	4,578,410	2,708,602
Investing Cash Flows
Additions to Oil and Gas Properties	(6,735,316)	(6,294,397)	(5,210,612)
Additions to Other Property, Plant and Equipment	(619,800)	(656,415)	(370,770)
Acquisition of Galveston LNG Inc.	0	0	(210,000)
Proceeds from Sales of Assets	1,309,776	1,433,137	672,593
Changes in Components of Working Capital Associated with Investing Activities	(73,923)	(237,267)	208,933
Other, Net	0	0	7,082
Net Cash Used in Investing Activities	(6,119,263)	(5,754,942)	(4,902,774)
Financing Cash Flows
Common Stock Sold	0	1,388,265	0
Long-Term Debt Borrowings	1,234,138	0	2,478,659
Long-Term Debt Repayments	0	(220,000)	(37,000)
Dividends Paid	(181,080)	(167,169)	(153,240)
Excess Tax Benefits from Stock-Based Compensation	67,035	0	0
Treasury Stock Purchased	(58,592)	(23,922)	(11,295)
Proceeds from Stock Options Exercised and Employee Stock Purchase Plan	82,887	35,913	34,560
Debt Issuance Costs	(1,578)	(4,787)	(8,300)
Repayment of Capital Lease Obligation	(2,824)	0	0
Other, Net	(235)	239	35
Net Cash Provided by Financing Activities	1,139,751	1,008,539	2,303,419
Effect of Exchange Rate Changes on Cash	3,444	(5,134)	(6,145)
Increase (Decrease) in Cash and Cash Equivalents	260,709	(173,127)	103,102
Cash and Cash Equivalents at Beginning of Period	615,726	788,853	685,751
Cash and Cash Equivalents at End of Period	$ 876,435	$ 615,726	$ 788,853