Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives - Effects of Derivatives Not Designated as Hedging Instruments on Consolidated Statements of Operations (Details)

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Fair Value Measurements and Derivatives - Effects of Derivatives Not Designated as Hedging Instruments on Consolidated Statements of Operations (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2020
Derivatives not designated as hedging instruments | Cash Flow Hedging | Other income (expense), net | Fuel contracts    
Derivative Instruments Gain Loss [Line Items]    
Amount of Gain (Loss) Recognized in Income $ 3,646 $ 3,646