This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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Investing Activities (Details) - USD ($) $ in Millions	3 Months Ended
Investing Activities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2016	Mar. 17, 2017
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	112
Investing income, interest	$ 272	18
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%
Gulfstream Natural Gas System, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	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%
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, interest		$ 18
Appalachia Midstream Services, LLC [Member] \| Williams Partners [Member]
Schedule of Equity Method Investments [Line Items]
Investments, Fair Value Disclosure	$ 1,100
Equity Method Investment, Summarized Financial Information [Abstract]
Fair Value Inputs, Discount Rate	9.50%