Fair Value of Financial Instruments - Non-Recurring Measurements (Table) (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents $ 118,454 $ 127,632
Restricted cash 2,978 6,558
Loan receivable from affiliate companies 31,588 30,112
Senior and ship mortgage notes (1,148,252) (1,181,838)
Long-term debt, including current portion (368,410) (389,332)
Long-term payable to affiliate companies (87,422) (76,872)
Fair Value, Measurements, Nonrecurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents 118,454 127,632
Restricted cash 2,978 6,558
Loan receivable from affiliate companies [1] 31,588 30,112
Senior and ship mortgage notes (1,148,252) (1,181,838)
Long-term debt, including current portion [2] (368,410) (389,332)
Long-term payable to affiliate companies [1] (87,422) (76,872)
(Level I) | Fair Value, Measurements, Nonrecurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents 118,454 127,632
Restricted cash 2,978 6,558
Senior and ship mortgage notes (1,148,252) (1,181,838)
(Level II) | Fair Value, Measurements, Nonrecurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Loan receivable from affiliate companies [1] 31,588 30,112
Long-term debt, including current portion [2] (368,410) (389,332)
Long-term payable to affiliate companies [1] $ (87,422) $ (76,872)
[1] The fair value of the Company’s loan receivable from/ payable to affiliate companies and long-term receivable from/payable to affiliate companies is estimated based on currently available debt with similar contract terms, interest rate and remaining maturities as well as taking into account the counterparty’s creditworthiness.
[2] The fair value of the Company’s long-term debt is estimated based on currently available debt with similar contract terms, interest rates and remaining maturities, published quoted market prices as well as taking into account the Company’s creditworthiness.