Fair Value Measurements and Disclosures - Fair Value of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity owned (units)	0		21,692,198
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in CNX Midstream Partners (0 Common Units and 21,692,198 Common Units, respectively)	$ 0		$ 70,000
Fair Value(1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in CNX Midstream Partners (0 Common Units and 21,692,198 Common Units, respectively)	$ 0		$ 364,000
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