Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Aggregate amount of acquisitions that will result in a temporary change in the Debt to EBITDA ratio requirement.

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Additional amount by which the credit facility can be increased.

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The maximum ratio of debt to capitalization (defined as net worth plus debt) permitted under the covenants.

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Maximum Ratio Of Debt To EBITDA permitted under covenants for the fiscal quarter and the two following fiscal quarters after an acquisition.

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Credit Facilities and Commercial Paper (Details) $ in Millions	Aug. 10, 2018 USD ($)	Feb. 19, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Williams Companies Inc [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 4,500		$ 4,500
Credit facility, loans outstanding			160	$ 270
Additional amount by which credit facility can be increased	$ 500
Maximum ratio of debt to EBITDA after acquisition	5.5
Acquisition Trigger Amount	$ 25
Williams Companies Inc [Member] \| SwingLineLoan [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	200
Williams Companies Inc [Member] \| Commercial paper [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 4,000
Commercial paper, outstanding			0	$ 0
Commercial paper, maximum maturity	397 days
Williams Companies Inc [Member] \| Commercial paper [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Commercial paper, outstanding		$ 0
Williams Companies Inc [Member] \| Letters of credit [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 1,000
Williams Companies Inc [Member] \| Letters Of Credit Under Certain Bilateral Bank Agreements [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, letters of credit outstanding			$ 14
Williams Partners L.P. [Member] \| Commercial paper [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	3,000
Transcontinental Gas Pipe Line Company, LLC [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 500
Maximum ratio of debt to capitalization	65.00%
Northwest Pipeline LLC [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 500
Maximum ratio of debt to capitalization	65.00%
Sep18Dec18Mar19Jun19 [Member] \| Williams Companies Inc [Member]
Credit Facility and Commercial Paper [Line Items]
Maximum ratio of debt to EBITDA	5.75
Sep19Dec19 [Member] \| Williams Companies Inc [Member]
Credit Facility and Commercial Paper [Line Items]
Maximum ratio of debt to EBITDA	5.5
Mar20 And Subsequent Quarters [Member] \| Williams Companies Inc [Member]
Credit Facility and Commercial Paper [Line Items]
Maximum ratio of debt to EBITDA	5.0