Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 400	$ 305	$ 400	$ 453
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Retained earnings related to undistributed earnings of equity method investees		90
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		12
Balance Sheet Information
Current Assets	313	390	313
Noncurrent Assets	1,390	588	1,390
Current Liabilities	149	171	149
Noncurrent Liabilities	256	90	256
Statements of Operations Information
Operating Revenues		790	667	645
Operating Expenses		303	355	393
Operating Income		487	312	252
Other (Income) Net		(15)	(7)	(9)
Income Before Income Taxes		502	319	261
Income Tax Provision		136	60	46
Net Income		$ 366	259	$ 215
Advantage Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments		50.00%
Equity Method Investments	0	$ 70	0
CONE Investments
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments		50.00%
Distributions from equity method investments	70
Equity Method Investments	172	$ 0	172
CONE Midstream
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments		34.00%
Atlantic Methanol Production Company
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments		45.00%
Alba Plant
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments		28.00%
Equity Method Investments	82	$ 80	82
AMPCO
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	120	129	120
Other
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 26	$ 26	$ 26