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Production Costs (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Production Costs [Line Items]    
Consumption of raw materials and consumables $ 311,812 $ 184,484
Employee compensation and benefits expense (1) 271,684 167,879
Contractors and outside services 117,018 88,475
Utilities 41,674 26,320
Other expenses 74,469 31,417
Changes in inventories 24,640 17,061
Production Costs 841,297 515,636
NRV adjustments to inventory $ (400) $ 24,300