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Financial Instruments - Interest Rate Risk (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Investments, All Other Investments [Abstract]      
Interest income, net $ 18,415 $ 27,969 $ 81
Impact of change in average variable rate, percent 1.49%    
Impact of change in average variable rate, amount $ (15,671)