Transactions with Affiliates (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($) employee	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) employee	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Related Party Transaction [Line Items]
Advances to affiliate		$ 541,052		$ 541,052		$ 811,693
Related party transaction, rate				0.83%
Entity number of employees | employee		0		0
Expenses, related party		$ 87,300	$ 73,400	$ 169,700	$ 156,300
Severance Costs					6,300
Cash distributions to parent				210,000	260,000
Cash contributions from parent				110,000	222,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Operating revenues, related party		3,100	2,900	6,400	4,100
Cost of natural gas sales, related party		800	200	1,900	1,500
Expenses, related party		(900)	$ (1,300)	(1,800)	$ (2,400)
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 541,100		$ 541,100		$ 811,700
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 120,000
Noncash distribution to Parent	$ 240,000