Fair Value Measurements - Commodity Swap Contracts (Details) - Not Designated as Hedging Instrument - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Commodity swap contracts | Minimum | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.76	1.71
Commodity swap contracts | Minimum | Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.79	0.76
Commodity swap contracts | Minimum | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.32	1.22
Commodity swap contracts | Maximum | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.88	1.79
Commodity swap contracts | Maximum | Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.16	1.16
Commodity swap contracts | Maximum | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.30	2.12
Commodity swap contracts | Weighted Average | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.81	1.75
Commodity swap contracts | Weighted Average | Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.91	0.89
Commodity swap contracts | Weighted Average | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.78	1.55
Fueling agreements | Minimum | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.76
Fueling agreements | Minimum | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.32
Fueling agreements | Maximum | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.88
Fueling agreements | Maximum | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.30
Fueling agreements | Weighted Average | ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.81
Fueling agreements | Weighted Average | Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.78