The expense charged against earnings during the period to allocate the capitalized costs of regulatory assets over the periods expected to benefit from such costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Other Income and Expenses (Details) - USD ($) $ in Millions				3 Months Ended		9 Months Ended
Other Income and Expenses (Details) - USD ($) $ in Millions	Mar. 28, 2018	Jul. 03, 2017	Feb. 23, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Gain on sale of Refinery Grade Propylene Splitter				$ 0	$ 1,095	$ 0	$ 1,095
Debt Instrument, Unamortized Discount (Premium), Net	$ 7	$ 3	$ 30
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	27	51	53
Debt Instrument, Unamortized Premium	34	54	23
Other income (expense) - net [Member] \| Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Amortization of regulatory assets associated with asset retirement obligations				8	8	24	25
Accrual of regulatory liability related to overcollection of certain employee expenses				5	5	16	16
Project development costs related to Constitution (see Note 3)				1	4	4	12
Gain on asset retirement				(10)	(5)	(10)	(5)
Regulatory Charge Resulting From Tax Rate Change				0	0	(10)	0
Other income (expense) - net [Member] \| West [Member]
Segment Reporting Information [Line Items]
Adjustments to regulatory liabilities related to Tax Reform				6	0	18	0
Regulatory Charge Resulting From Tax Rate Change				0	0	(7)	0
Gains on contract settlements and terminations				0	0	0	(15)
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				(37)	0	(37)	0
Gain on sale of Refinery Grade Propylene Splitter				0	0	0	(12)
Selling, general, and administrative expenses [Member] \| Other [Member]
Segment Reporting Information [Line Items]
Noncash Contribution Expense				35
WPZ Merger				15		19
Severance and other related costs					5		18
Other Nonoperating Income (Expense) [Member] \| Atlantic Gulf [Member]
Segment Reporting Information [Line Items]
Allowance for funds used during construction, capitalized cost of equity				33	17	80	55
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				22	8	31	44
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	$ (12)	$ 0
4.875% Senior Unsecured Notes due 2024 [Member]
Segment Reporting Information [Line Items]
Long-term debt retired	$ 750
Long-term debt interest rate	4.875%
4.875% Senior Unsecured Notes due 2023 [Member]
Segment Reporting Information [Line Items]
Long-term debt retired		$ 1,400
Long-term debt interest rate		4.875%
6.125% Senior Unsecured Notes due 2022 [Member]
Segment Reporting Information [Line Items]
Long-term debt retired			$ 750
Long-term debt interest rate			6.125%