Derivative Financial Instruments and Fair Value Measurements - Derivatives Recorded at Fair Value in Consolidated Balance Sheets (Details) - Not designated as hedging instruments - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 190	$ 11
Derivative Liabilities	1,070	4,328
Current | Commodities contracts
Derivatives, Fair Value [Line Items]
Derivative Assets	190	11
Derivative Liabilities	1,070	4,328
Non-current | Commodities contracts
Derivatives, Fair Value [Line Items]
Derivative Assets	0	0
Derivative Liabilities	$ 0	$ 0