Transactions with Affiliates (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) employee	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) employee	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Advances to affiliate		$ 795,853		$ 795,853		$ 64,608
Related party transaction, rate				0.25%
Entity number of employees | employee		0		0
Expenses, related party		$ 73,400	$ 81,600	$ 156,300	$ 162,600
Severance Costs				6,300
Cash distributions to parent				260,000	233,000
Cash contributions from parent				222,000	312,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Operating revenues, related party		2,900	700	4,100	1,900
Cost of natural gas sales, related party		200	1,700	1,500	4,200
Expenses, related party		(1,300)	$ (1,500)	(2,400)	$ (2,700)
Williams Partners L.P. [Member]
Related Party Transaction [Line Items]
Advances to affiliate		$ 795,900		$ 795,900		$ 64,600
Subsequent Event [Member]
Related Party Transaction [Line Items]
Cash distributions to parent	$ 90,000
Cash contributions from parent	$ 150,000