Debt and Banking Arrangements Long-Term Debt Issuances and Retirements (Details 1) - USD ($) $ in Millions						9 Months Ended
	Jul. 06, 2017	Jul. 03, 2017	Apr. 15, 2017	Feb. 23, 2017	Feb. 01, 2017	Sep. 30, 2017	Jun. 05, 2017	Apr. 03, 2017
Transcontinental Gas Pipe Line Company, LLC [Member]
Debt Instrument [Line Items]
Other Long-term Debt, Noncurrent						$ 237
Debt Instrument, Term						35 years
Variable Interest Term Loan due 2018 [Member] | Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Long-term debt retired	$ 850
3.75% Senior Notes Due 2027 [Member] | Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Long-term debt face amount							$ 1,450
Long-term debt interest rate							3.75%
4.875% Senior Unsecured Notes due 2023 [Member] | Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Long-term debt interest rate		4.875%
Long-term debt retired		$ 1,400
6.125% Senior Unsecured Notes due 2022 [Member] | Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Long-term debt interest rate				6.125%
Long-term debt retired				$ 750
4% Senior Unsecured Notes Due 2027 [Member] | Northwest Pipeline LLC [Member]
Debt Instrument [Line Items]
Long-term debt face amount								$ 250
Long-term debt interest rate								4.00%
Additional interest rate accrued for default of registration rights agreements first period								0.25%
Additional interest rate accrued for default of registration rights agreements each subsequent period								0.25%
Maximum additional interest rate accrued for default of registration rights agreements all periods								0.50%
5.95% Senior Unsecured Notes due 2017 [Member] | Northwest Pipeline LLC [Member]
Debt Instrument [Line Items]
Long-term debt interest rate			5.95%
Long-term debt retired			$ 185
7.25% Senior Unsecured Notes due 2017 [Member] | Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Long-term debt interest rate					7.25%
Long-term debt retired					$ 600