Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current Assets
Cash and Cash Equivalents	$ 1,387	$ 1,455
Accounts Receivable, Net	964	783
Other Current Assets	420	180
Total Current Assets	2,771	2,418
Property, Plant and Equipment
Oil and Gas Properties (Successful Efforts Method of Accounting)	19,496	19,057
Property, Plant and Equipment, Other	344	294
Total Property, Plant and Equipment, Gross	19,840	19,351
Accumulated Depreciation, Depletion and Amortization	(6,289)	(6,569)
Total Property, Plant and Equipment, Net	13,551	12,782
Goodwill	635	696
Other Noncurrent Assets	597	548
Total Assets	17,554	16,444
Current Liabilities
Accounts Payable - Trade	1,508	1,343
Other Current Liabilities	1,024	925
Total Current Liabilities	2,532	2,268
Long-Term Debt	3,736	4,100
Deferred Income Taxes, Noncurrent	2,218	2,059
Other Noncurrent Liabilities	810	752
Total Liabilities	9,296	9,179
Commitments and Contingencies
Shareholders Equity [Abstract]
Preferred Stock - Par Value $1.00 per share; 4 Million Shares Authorized, None Issued	0	0
Common Stock - Par Value $0.01 and $3.33 1/3 per share; 500 Million and 250 Million Shares Authorized; 198 Million and 197 Million Shares Issued, Respectively	2	656
Additional Paid in Capital	3,304	2,497
Accumulated Other Comprehensive Loss	(113)	(100)
Treasury Stock, at Cost; 19 Million Shares	(648)	(638)
Retained Earnings	5,713	4,850
Total Shareholders’ Equity	8,258	7,265
Total Liabilities and Shareholders’ Equity	$ 17,554	$ 16,444