Investing Activities (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Equity Method Investments	$ 0	$ 200
Gain from sale of an equity-method investment interest	0	269
Investing income, nonoperating	$ 4	$ 272
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%
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
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
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%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
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Amount of gain (loss) on sale or disposal of an equity method investment.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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The aggregate amount of income from investments (for example, dividends) not considered a component of the entity's core operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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