Other Income and Expenses (Details) - USD ($) $ in Millions					12 Months Ended
		Mar. 28, 2018	Jul. 03, 2017	Feb. 23, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gains on asset retirements	[1]				$ 39	$ 22
Regulatory Charges In Operating Expense Resulting From Tax Reform					(17)	674	$ 0
Gain on sale of Refinery Grade Propylene Splitter					692	1,095	0
Service revenues					8,604
Regulatory charges resulting from Tax Reform (Note 1)					(15)	776	0
Repayments of Long-term Debt					3,204	5,925	7,091
Debt Instrument, Unamortized Discount (Premium), Net		$ 7	$ 3	$ 30	62	24
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums		27
Debt Instrument, Unamortized Premium		$ 34
Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Litigation Settlement, Amount Awarded to Other Party							15
Other income (expense) - net [Member] | Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Amortization of regulatory assets associated with asset retirement obligations					33	33	33
Accrual of regulatory liability related to overcollection of certain employee expenses					22	22	25
Project development costs					4	16	28
Gains on asset retirements					(12)	0	(11)
Other income (expense) - net [Member] | West [Member]
Segment Reporting Information [Line Items]
Gains on contract settlements and terminations					0	(15)	0
Regulatory Charges In Operating Expense Resulting From Tax Reform					24	0	0
Other income (expense) - net [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Gain on sale of Refinery Grade Propylene Splitter					0	(12)	0
Net foreign currency exchange (gains) losses (1)	[2]				0	0	10
Gain on sale of unused pipe					0	0	(10)
Regulatory Benefit Resulting From Tax Rate Change					(37)	0	0
Selling, general and administrative expenses [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Project development costs							61
Noncash Contribution Expense					35
WPZ Merger					20
Selling, general and administrative expenses [Member] | Corporate and Other [Member] | Acquisition and Merger [Member]
Segment Reporting Information [Line Items]
Restructuring Charges						9	47
Service revenues [Member]
Segment Reporting Information [Line Items]
Deferred Revenue, Revenue Recognized							173
Selling, general, and administrative expenses and Operating and maintenance expenses [Member]
Segment Reporting Information [Line Items]
Severance and other related costs						22	$ 42
Restructuring and Related Cost, Number of Positions Eliminated, Period Percent							10.00%
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | Northeast G And 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							13
Selling, general, and administrative expenses and Operating and maintenance expenses [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Severance and other related costs							18
Other income (expense) - net [Member]
Segment Reporting Information [Line Items]
Regulatory charges resulting from Tax Reform (Note 1)						102
Other income (expense) - net [Member] | Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity					89	71	66
Regulatory charges resulting from Tax Reform (Note 1)						33
Other income (expense) - net [Member] | West [Member]
Segment Reporting Information [Line Items]
Regulatory charges resulting from Tax Reform (Note 1)						6
Other income (expense) - net [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Regulatory charges resulting from Tax Reform (Note 1)						63
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums			51	53
Debt Instrument, Unamortized Premium			$ 54	$ 23
Deferred taxes on equity funds used during construction [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity					35	52	23
Disposal Group, Not Discontinued Operations [Member] | Canadian Operations [Member] | Other income (expense) - net [Member]
Segment Reporting Information [Line Items]
Loss on sale of Canadian operations (Note 3)							66
Disposal Group, Not Discontinued Operations [Member] | Canadian Operations [Member] | Other income (expense) - net [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Loss on sale of Canadian operations (Note 3)					0	5	66
Pension Plan [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					(23)	(71)	(2)
Pension Plan [Member] | Other income (expense) - net [Member] | Northeast G And P [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					4	7
Pension Plan [Member] | Other income (expense) - net [Member] | Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					7	15
Pension Plan [Member] | Other income (expense) - net [Member] | West [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					6	13
Pension Plan [Member] | Other income (expense) - net [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					5	35
Pension Plan [Member] | Other income (expense) - net [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement					(23)	(71)
Northwest Pipeline LLC [Member] | Other income (expense) - net [Member] | West [Member]
Segment Reporting Information [Line Items]
Regulatory charge resulting from tax rate change					$ 12	$ 0	$ 0
4.875% Senior Unsecured Notes due 2024 [Member]
Segment Reporting Information [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.875%
Extinguishment of Debt, Amount		$ 750
6.125% Senior Unsecured Notes due 2022 [Member]
Segment Reporting Information [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				6.125%
Extinguishment of Debt, Amount				$ 750
4.875% Senior Unsecured Notes due 2023 [Member]
Segment Reporting Information [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.875%
Extinguishment of Debt, Amount			$ 1,400

[1] (2)Several factors are considered in the annual review process, including inflation rates, current estimates for removal cost, market risk premiums, discount rates, and the estimated remaining useful life of the assets. The 2018 revisions reflect changes in removal cost estimates, decreases in the estimated remaining useful life of certain assets and increases in the discount rates used in the annual review process. The 2017 revisions reflect changes in removal cost estimates and decreases in the estimated remaining useful life of certain assets and discount rates used in the annual review process.

[2] ____________(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 3 – Divestitures).