Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Three vessels    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Impairment loss $ 59,108 $ 92,013
Chartered-in vessels    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Impairment loss $ 1,361 $ 38,636