Equity Method Investments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments (in hundredths)		50.00%
Equity Method Investments	$ 367	$ 329	$ 285
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Retained earnings related to undistributed earnings of equity method investees	111
AMPCO Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Difference between the carrying value of an equity method investment and the underlying net assets of the investee	10
Balance Sheet Information
Current Assets	384	374
Noncurrent Assets	902	827
Current Liabilities	348	360
Noncurrent Liabilities	24	16
Statements of Operations Information
Operating Revenues	1,173	1,139	809
Operating Expenses	361	335	296
Operating Income	812	804	513
Other (Income), Net	(5)	(12)	(12)
Income Before Income Taxes	817	816	525
Income Tax Provision	200	201	133
Net Income	617	615	392
AMPCO [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments (in hundredths)	45.00%
Equity Method Investments	137	147
Alba Plant [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments (in hundredths)	28.00%
Equity Method Investments	93	96
CONE Gathering LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments (in hundredths)	50.00%
Equity Method Investments	121	72
Other Investees [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 16	$ 14