Other Income and Expenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 28, 2018
Segment Reporting Information [Line Items]
Tangible Asset Impairment Charges			$ 76	$ 64
Severance and other related costs	$ 10		53
Northeast G And P [Member]
Segment Reporting Information [Line Items]
Severance and other related costs	(3)		7
Other [Member]
Segment Reporting Information [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	0	$ 0	0	0	$ (7)
West [Member]
Segment Reporting Information [Line Items]
Severance and other related costs	2		16
Atlantic Gulf Midstream [Member]
Segment Reporting Information [Line Items]
Severance and other related costs	11		30
Operating Expense [Member]
Segment Reporting Information [Line Items]
Severance and other related costs	7		30
Other income (expense) - net [Member] | Other [Member]
Segment Reporting Information [Line Items]
Benefit of regulatory asset associated with increase in Transco's estimated deferred state income tax rate following WPZ Merger	0	(37)	12	(37)
Other income (expense) - net [Member] | Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Amortization of regulatory assets associated with asset retirement obligations	1	8	17	24
Accrual of regulatory liability related to overcollection of certain employee expenses	(9)	5	(11)	16
Adjustments to regulatory liabilities related to Tax Reform	0	0	0	(10)
Reversal of expenditures previously capitalized	0	0	10	0
Regulatory Charge Resulting From Tax Rate Change	(12)	0	(19)	0
Gain on asset retirement	0	(10)	0	(10)
Other income (expense) - net [Member] | West [Member]
Segment Reporting Information [Line Items]
Tangible Asset Impairment Charges	0	12	0	12
Adjustments to regulatory liabilities related to Tax Reform	0	0	0	(7)
Regulatory Charge Resulting From Tax Rate Change	6	6	18	18
Selling, general, and administrative expenses [Member]
Segment Reporting Information [Line Items]
Severance and other related costs	3		23
Selling, general, and administrative expenses [Member] | Other [Member]
Segment Reporting Information [Line Items]
Noncash Contribution Expense	0	35	0	35
WPZ Merger	0	15	0	19
Other Nonoperating Income (Expense) [Member] | Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity	9	32	21	78
Deferred Taxes On Equity Funds Used During Construction [Member] | Other [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity	$ 3	$ 19	$ 7	$ 28