Exit Cost - Transportation Commitments - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Long-term Purchase Commitment [Line Items]
Commitment amount		$ 1,000
Reduction and offset of financial obligations		38	$ 8
Commitment reduction	$ 350
Marcellus Shale Firm Transportation Obligations
Long-term Purchase Commitment [Line Items]
Marcellus exit cost accrual	$ 92	$ 88	$ 0
Minimum
Long-term Purchase Commitment [Line Items]
Term		3 years
Maximum
Long-term Purchase Commitment [Line Items]
Term		14 years