Other Income and Expenses (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other income (expense) - net [Member] | Atlantic-Gulf [Member]
Segment Reporting Information [Line Items]
Amortization of regulatory assets associated with asset retirement obligations		$ 8		$ 8	$ 25	$ 25
Accrual of regulatory liability related to overcollection of certain employee expenses		6		5	19	15
Project development costs related to Constitution (see Note 3)		11		0	19	0
Other income (expense) - net [Member] | NGL & Petchem Services [Member]
Segment Reporting Information [Line Items]
Net foreign currency exchange (gains) losses (1)	[1]	0		(4)	11	(8)
Selling, general, and administrative expenses [Member] | Central [Member]
Segment Reporting Information [Line Items]
Business combination, merger related costs				1	5	35
Operating and maintenance expenses [Member] | Central [Member]
Segment Reporting Information [Line Items]
Business combination, integration related costs						10
Selling, general, and administrative expenses and Operating and maintenance expenses [Member]
Segment Reporting Information [Line Items]
Approximate percentage of workforce reductions			10.00%
Severance and other related costs					25
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | Central [Member]
Segment Reporting Information [Line Items]
Severance and other related costs					6
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | Northeast G&P [Member]
Segment Reporting Information [Line Items]
Severance and other related costs					3
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | Atlantic-Gulf [Member]
Segment Reporting Information [Line Items]
Severance and other related costs					8
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | West [Member]
Segment Reporting Information [Line Items]
Severance and other related costs					4
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | NGL & Petchem Services [Member]
Segment Reporting Information [Line Items]
Severance and other related costs					4
Interest incurred [Member]
Segment Reporting Information [Line Items]
Business combination, merger related costs						2
Service revenues [Member] | Atlantic-Gulf [Member]
Segment Reporting Information [Line Items]
Revenue adjustment associated with litigation					15
Net insurance recoveries - Geismar incident [Member] | NGL & Petchem Services [Member] | Geismar Incident [Member]
Segment Reporting Information [Line Items]
Insurance recoveries						126
Other income (expense) - net [Member]
Segment Reporting Information [Line Items]
Gain on extinguishment of debt						14
Other income (expense) - net [Member] | Atlantic-Gulf [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity		17		20	46	56
Disposal Group, Not Discontinued Operations [Member] | Canadian Operations [Member] | Other income (expense) - net [Member] | NGL & Petchem Services [Member]
Segment Reporting Information [Line Items]
Loss on sale of Canadian operations (see Note 2)		$ 32		$ 0	$ 32	$ 0

[1] Primarily relates to gains and losses incurred on foreign currency transactions and the remeasurement of U.S. dollar denominated current assets and liabilities within our former Canadian operations (see Note 2 – Divestiture).