Fair Value Measurements and Disclosures - Fair Value of Equity Method Investments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity owned (units)	21,692,198	21,692,198
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in CNX Midstream Partners (21,692,198 Units)	$ 72	$ 70
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in CNX Midstream Partners (21,692,198 Units)	$ 399	$ 364