Transactions with Affiliates (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) employee	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) employee	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Advances to affiliate		$ 51,741		$ 51,741		$ 171,867
Related party transaction, rate				0.27%
Entity number of employees | employee		0		0
Related party transaction, expenses from transactions with related party		$ 22,800	$ 24,100	$ 68,900	$ 74,500
Severance and other related costs				2,000
Cash distributions to parent				131,000	$ 129,000
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 51,700		$ 51,700		$ 171,900
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 43,000