Variable Interest Entities (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets	$ 44,320	$ 46,040
Variable Interest Entity, Primary Beneficiary [Member] | Cash and cash equivalents [Member]
Variable Interest Entity [Line Items]
Assets	62	102
Variable Interest Entity, Primary Beneficiary [Member] | Trade accounts and other receivables - net [Member]
Variable Interest Entity [Line Items]
Assets	150	167
Variable Interest Entity, Primary Beneficiary [Member] | Other current assets and deferred charges [Member]
Variable Interest Entity [Line Items]
Assets	6	5
Variable Interest Entity, Primary Beneficiary [Member] | Property, plant, and equipment - net [Member]
Variable Interest Entity [Line Items]
Assets	5,562	5,745
Variable Interest Entity, Primary Beneficiary [Member] | Intangible assets - net of accumulated amortization [Member]
Variable Interest Entity [Line Items]
Assets	2,404	2,669
Variable Interest Entity, Primary Beneficiary [Member] | Regulatory assets, deferred charges, and other [Member]
Variable Interest Entity [Line Items]
Assets	12	13
Variable Interest Entity, Primary Beneficiary [Member] | Accounts payable [Member]
Variable Interest Entity [Line Items]
Liabilities	(27)	(58)
Variable Interest Entity, Primary Beneficiary [Member] | Accrued liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities	(36)	(66)
Variable Interest Entity, Primary Beneficiary [Member] | Regulatory liabilities, deferred income, and other [Member]
Variable Interest Entity [Line Items]
Liabilities	$ (287)	$ (283)
Variable Interest Entity, Primary Beneficiary [Member] | Northeast JV [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	65.00%
Variable Interest Entity, Primary Beneficiary [Member] | Gulfstar One [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	51.00%
Variable Interest Entity, Primary Beneficiary [Member] | Cardinal Gas Services LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	66.00%
Variable Interest Entity, Not Primary Beneficiary [Member] | Brazos Permian II LLC [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	15.00%