Fair Value Measurements and Disclosures - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 14, 2018	Feb. 01, 2018	Jan. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity owned (units)	0				0					21,692,198
Asset Impairments	$ 0			$ 0	$ 168	$ 0
CONE Gathering LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares sold (in shares)	14,200,000	7,500,000
Ownership	22.30%				22.30%			34.10%	50.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Tamar and Dalit Fields
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount percent							15.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Gulf of Mexico Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairments			$ 168		$ 168
CNX Midstream Partners
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity owned (units)								21,700,000