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Investing Activities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Investing Activities (Details) - USD ($) $ in Millions	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Jun. 01, 2016	Nov. 01, 2015
Schedule of Equity Method Investments [Line Items]
Impairment of equity-method investments	$ 0	$ 0	$ 112	$ 0
Investing income, interest	18	9	36	9
Equity earnings (losses)	101	$ 93	198	144
Contribution to Gulfstream for repayment of debt			148	0
Delaware Basin Gas Gathering System [Member]
Schedule of Equity Method Investments [Line Items]
Impairment of equity-method investments			59
Laurel Mountain Midstream, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Impairment of equity-method investments			50
Gulfstream Natural Gas System, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Special distribution from Gulfstream					$ 396
Contribution to Gulfstream for repayment of debt			148		248
Equity-method investment debt						$ 300	$ 500
Former Venezuela Operations [Member]
Schedule of Equity Method Investments [Line Items]
Investing income, interest	18		36	$ 9
Carrying Amount [Member] \| Former Venezuela Operations [Member]
Schedule of Equity Method Investments [Line Items]
Notes Receivable, Fair Value Disclosure	$ 0		$ 0		$ 0