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Long Term Debt - Additional Information - Other (Details) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Debt Instruments [Abstract]    
Weighted-average effective interest rate 4.20% 4.60%
Aggregate annual long-term principal repayments, 2019 $ 25.4  
Aggregate annual long-term principal repayments, 2020 101.8  
Aggregate annual long-term principal repayments, 2021 426.6  
Aggregate annual long-term principal repayments, 2022 $ 59.1