Segment Disclosures Reconciliation of Segment Modified EBITDA to Consolidated Net Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Modified EBITDA to Net Income (Loss):
Modified EBITDA Earnings (Loss)	$ 939	$ 1,003	$ 3,148	$ 2,095
Accretion expense associated with asset retirement obligations for nonregulated operations	(7)	(9)	(23)	(24)
Depreciation and amortization expenses	(433)	(435)	(1,308)	(1,326)
Equity earnings (losses)	115	104	347	302
Impairment of equity-method investments	0	0	0	112
Other investing income (loss) – net	(4)	(28)	(278)	(64)
Proportional Modified EBITDA of equity-method investments	(202)	(194)	(611)	(574)
Interest expense	(267)	(297)	(818)	(886)
(Provision) benefit for income taxes	(24)	(69)	(126)	74
Net income (loss)	125	131	887	(387)
Operating Segments [Member] | Williams Partners [Member]
Reconciliation of Modified EBITDA to Net Income (Loss):
Modified EBITDA Earnings (Loss)	1,000	1,070	3,208	2,629
Operating Segments [Member] | Other [Member]
Reconciliation of Modified EBITDA to Net Income (Loss):
Modified EBITDA Earnings (Loss)	$ (61)	$ (67)	$ (60)	$ (534)