Acquisitions (Details) - USD ($) $ in Millions				1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 18, 2019	Dec. 31, 2018		Jun. 30, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 18, 2020	Mar. 17, 2019
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 18)								$ 1,046	$ 186	$ 32
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life								30 years
Changes in ownership of consolidated subsidiaries, net									141	(4)
Impairment of goodwill (Note 18)								$ 187	0	0
Northeast JV [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners				35.00%
Noncontrolling Interests [Member]
Business Acquisition [Line Items]
Changes in ownership of consolidated subsidiaries, net									567	(18)
Impairment of goodwill (Note 18)					$ 65
Capital in excess of par value [Member]
Business Acquisition [Line Items]
Changes in ownership of consolidated subsidiaries, net									(426)	14
Northeast JV [Member]
Business Acquisition [Line Items]
Noncontrolling Interest in Joint Ventures				$ 1,330
Increase (Decrease) in Deferred Income Taxes									(141)
Northeast JV [Member] | Noncontrolling Interests [Member]
Business Acquisition [Line Items]
Changes in ownership of consolidated subsidiaries, net									567
Northeast JV [Member] | Capital in excess of par value [Member]
Business Acquisition [Line Items]
Changes in ownership of consolidated subsidiaries, net									(426)
Williams Companies Inc [Member] | Northeast JV [Member]
Business Acquisition [Line Items]
Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest				65.00%
Selling, general and administrative expenses [Member] | Northeast JV [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs									6
Northeast G And P [Member]
Business Acquisition [Line Items]
Goodwill		$ 0					$ 188	0	188	0
Level 3 [Member] | Fair Value, Nonrecurring [Member]
Business Acquisition [Line Items]
Impairment of goodwill (Note 18)					187
Level 3 [Member] | Fair Value, Nonrecurring [Member] | Impairment Of Equity-Method Investments [Member]
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 18)									(1)
Utica East Ohio Midstream, LLC Acquisition [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 741
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	56
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	1,387
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	328
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	1,771
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	1,764
Goodwill	187										$ 187
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	1,951
Business Acquisition, Goodwill, Expected Tax Deductible Amount	$ 187
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	20 years
Percentage Of Finite Lived Intangible Assets Impacted By Our Intent Or Ability To Renew Or Extend Arrangement	49.00%
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							179
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual							53
Goodwill, Other Increase (Decrease)					$ 1			$ 1
Utica East Ohio Midstream, LLC Acquisition [Member] | Pro Forma [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue									8,233	8,836
Business Acquisition, Pro Forma Net Income (Loss)									$ 928	$ (128)
Utica East Ohio Midstream, LLC Acquisition [Member] | Selling, general and administrative expenses [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs							$ 4
Utica East Ohio Midstream, LLC [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage		62.00%								62.00%
Utica East Ohio Midstream, LLC [Member] | Level 3 [Member] | Fair Value, Nonrecurring [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Business Acquisition [Line Items]
Impairment of equity-method investments (Note 18)		$ 32	[1]			$ 74
Utica East Ohio Midstream, LLC [Member] | Utica East Ohio Midstream, LLC Acquisition [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] The estimated fair value at March 17, 2019, 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 3 – Acquisitions and Divestitures). These inputs resulted in a fair value measurement within Level 2 of the fair value hierarchy. The estimated fair value at December 31, 2018, was determined by a market approach based on our analysis of inputs in the principal market.