Derivatives - Derivative Activity (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) institution	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) institution	Jun. 30, 2019 USD ($)
Derivative Instruments and Hedging Activities Disclosure
(Gain) loss on derivative contracts	$ (2,241)	$ 0	$ (12,467)	$ 209
Cash received on settlements			$ (10,577)	(5,078)
Number of counterparties to open derivative contracts | institution	2		2
Commodity derivative contracts
Derivative Instruments and Hedging Activities Disclosure
(Gain) loss on derivative contracts	$ 2,241	0	$ (12,467)	209
Cash received on settlements	$ 6,490	$ 0	$ 10,577	$ 5,078