Fair Value Measurements - Fair Value Recognition - Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commodity swap contracts
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Beginning balance	$ 10,332
Settlements, net	667
Total gain (loss)	7,729	$ (10,332)
Ending balance	3,270	10,332
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(7,062)	$ 10,332
Embedded derivatives
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Total gain (loss)	723
Ending balance	723
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 723