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Investing Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Investing Activities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Equity Method Investments			$ 200	$ 0
Gain from sale of an equity-method investment interest			269	0
Impairment of equity-method investments	$ 0	$ 0	0	112
Investing income, nonoperating	$ 4	28	$ 278	64
Delaware Basin Gas Gathering System [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					50.00%
Laurel Mountain Midstream, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	69.00%		69.00%
Gulfstream Natural Gas System, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Williams Partners [Member] \| Delaware Basin Gas Gathering System [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					50.00%
Proceeds from Sale of Equity Method Investments			$ 155
Gain from sale of an equity-method investment interest			$ 269
Impairment of equity-method investments				59
Williams Partners [Member] \| Appalachia Midstream Services, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	66.00%		66.00%
Williams Partners [Member] \| Appalachia Midstream Services, LLC [Member] \| Other investing income (loss) - net [Member]
Schedule of Equity Method Investments [Line Items]
Gain from sale of an equity-method investment interest		$ 27		27
Williams Partners [Member] \| Ranch Westex JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Equity Method Investments			$ 45
Williams Partners [Member] \| Laurel Mountain Midstream, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Impairment of equity-method investments				50
Former Venezuela Operations [Member]
Schedule of Equity Method Investments [Line Items]
Investing income, nonoperating				$ 36
Appalachia Midstream Services, LLC [Member] \| Williams Partners [Member]
Schedule of Equity Method Investments [Line Items]
Investments, Fair Value Disclosure	$ 1,100		$ 1,100
Equity Method Investment, Summarized Financial Information [Abstract]
Fair Value Inputs, Discount Rate			9.50%