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		$ 719,960		$ 811,693
Related party transaction, rate		0.57%
Entity number of employees | employee		0
Expenses, related party		$ 82,400	$ 82,900
Severance Costs			6,300
Cash distributions to parent		100,000	175,000
Cash contributions from parent		110,000	112,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Operating revenues, related party		3,300	1,200
Cost of natural gas sales, related party		1,100	1,300
Expenses, related party		(900)	$ (1,100)
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 720,000		$ 811,700
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 110,000