Financial Instruments - Summary of Outstanding Commodity Derivative Contracts (Details)	3 Months Ended
	Mar. 31, 2020 $ / gal gal
Benzene Swaps
Derivative [Line Items]
Type	Benzene swaps
Unit of measure	U.S. liquid gallon
Contracted volume | gal	1,340,608
Contracted date of maturity, start	2020-06
Contracted date of maturity, end	2020-09
Benzene Swaps | Minimum
Derivative [Line Items]
Contracted price range	2.15
Benzene Swaps | Maximum
Derivative [Line Items]
Contracted price range	2.59
Diesel Swaps
Derivative [Line Items]
Type	Diesel swaps
Unit of measure	U.S. liquid gallon
Contracted volume | gal	3,540,349
Contracted date of maturity, start	2020-05
Contracted date of maturity, end	2021-03
Diesel Swaps | Minimum
Derivative [Line Items]
Contracted price range	2.50
Diesel Swaps | Maximum
Derivative [Line Items]
Contracted price range	3.17