Transactions with Affiliates (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2016 USD ($)	Mar. 31, 2016 USD ($) employee	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Advances to affiliate		$ 198,021		$ 171,867
Related party transaction, rate		0.22%
Entity number of employees | employee		0
Related party transaction, expenses from transactions with related party		$ 25,000	$ 25,400
Severance and other related costs		2,000
Cash distributions to parent		57,000	$ 58,000
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 198,000		$ 171,900
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 29,000