Transactions with Affiliates (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) employee	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Related Party Transaction [Line Items]
Advances to affiliate		$ 69,184		$ 45,137
Related party transaction, rate		0.57%
Entity number of employees | employee		0
Related party transaction, expenses from transactions with related party		$ 23,000	$ 25,000
Severance and other related costs			2,000
Cash distributions to parent		50,000	$ 57,000
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 69,200		$ 45,100
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 57,000