Acquisitions (Details) - USD ($) $ in Millions				3 Months Ended
		Mar. 31, 2019	Mar. 18, 2019	Mar. 31, 2019	Mar. 31, 2018	Mar. 17, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 2)				$ 74	$ 0
Scenario, Plan [Member] | Ohio Valley Midstream LLC [Member]
Business Acquisition [Line Items]
Noncontrolling Interest in Joint Ventures		$ 1,304		$ 1,304
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		35.00%		35.00%
Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest				65.00%
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 2)	[1]			$ 74
Utica East Ohio Midstream, LLC [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage							62.00%
Utica East Ohio Midstream, LLC [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 2)				74
Utica East Ohio Midstream, LLC Acquisition [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			$ 740
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net			0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			13
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets			52
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			1,493
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			389
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			1,934
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities			4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			1,930
Goodwill			19
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			1,949
Business Acquisition, Goodwill, Expected Tax Deductible Amount			$ 19
Finite-Lived Intangible Assets, Remaining Amortization Period			20 years
Percentage Of Finite Lived Intangible Assets Impacted By Our Intent Or Ability To Renew Or Extend Arrangement			34.00%
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension			10 years
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 6
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 2
Utica East Ohio Midstream, LLC Acquisition [Member] | Pro Forma [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue				2,086	2,121
Business Acquisition, Pro Forma Net Income (Loss)				273	$ 155
Utica East Ohio Midstream, LLC Acquisition [Member] | Selling, general, and administrative expenses [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs				$ 3
Utica East Ohio Midstream, LLC Acquisition [Member] | Utica East Ohio Midstream, LLC [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired			38.00%
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage						62.00%

[1] Relates to Northeast G&P’s equity-method investment in UEOM. The estimated fair value was determined by a market approach based on the transaction price for the purchase of the remaining interest in UEOM as finalized just prior to the signing and closing of the acquisition in March 2019 (see Note 2 – Acquisitions). This impairment is reported in Impairment of equity-method investments in the Consolidated Statement of Income.