Consolidated Statements of Operations (unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues
Oil, Gas and NGL Sales	$ 1,083	$ 1,037
Income from Equity Method Investees	60	51
Total	1,143	1,088
Costs and Expenses
Production Expense	187	163
Exploration Expense	61	60
Depreciation, Depletion and Amortization	366	294
General and Administrative	112	97
Other Operating (Income) Expense, Net	(8)	12
Total	718	626
Operating Income	425	462
Other (Income) Expense
Loss on Commodity Derivative Instruments	72	96
Interest, Net of Amount Capitalized	25	32
Other Non-Operating (Income) Expense, Net	10	(1)
Total	107	127
Income from Continuing Operations Before Income Taxes	318	335
Income Tax Provision	86	86
Income from Continuing Operations	232	249
Discontinued Operations, Net of Tax	29	14
Net Income	$ 261	$ 263
Earnings Per Share, Basic [Abstract]
Income from Continuing Operations (in dollars per share)	$ 1.29	$ 1.40
Discontinued Operations, Net of Tax (in dollars per share)	$ 0.17	$ 0.08
Net Income (in dollars per share)	$ 1.46	$ 1.48
Earnings Per Share, Diluted [Abstract]
Income from Continuing Operations (in dollars per share)	$ 1.28	$ 1.39
Discontinued Operations, Net of Tax (in dollars per share)	$ 0.17	$ 0.08
Net Income (in dollars per share)	$ 1.45	$ 1.47
Weighted Average Number of Shares Outstanding, Basic (in shares)	179	177
Weighted Average Number of Shares Outstanding, Diluted (in shares)	181	180