Fair Value of Financial Instruments - Non-Recurring Measurements (Table) (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents $ 127,632 $ 135,992
Restricted cash 6,558 5,386
Investments in available-for-sale securities 238 0
Loan receivable from affiliate companies 30,112 23,008
Long-term receivable from affiliate companies 0 11,105
Senior and ship mortgage notes (1,181,838) (974,170)
Capital lease obligations, including current portion 0 (17,617)
Long-term debt, including current portion (389,332) (308,080)
Loan payable to affiliate company 0 (51,240)
Long-term payable to affiliate companies (76,872) (6,399)
Fair Value, Measurements, Nonrecurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents 127,632 135,992
Restricted cash 6,558 5,386
Investments in available-for-sale securities 238  
Loan receivable from affiliate companies [1] 30,112 23,008
Long-term receivable from affiliate companies [1]   11,105
Senior and ship mortgage notes (1,181,838) (974,170)
Capital lease obligations, including current portion [2]   (17,617)
Long-term debt, including current portion [2] (389,332) (308,080)
Loan payable to affiliate company [1]   (51,240)
Long-term payable to affiliate companies [1] (76,872) (6,399)
(Level I) | Fair Value, Measurements, Nonrecurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents 127,632 135,992
Restricted cash 6,558 5,386
Investments in available-for-sale securities 238  
Senior and ship mortgage notes (1,181,838) (974,170)
(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] 30,112 23,008
Long-term receivable from affiliate companies [1]   11,105
Capital lease obligations, including current portion [2]   (17,617)
Long-term debt, including current portion [2] (389,332) (308,080)
Loan payable to affiliate company [1]   (51,240)
Long-term payable to affiliate companies [1] $ (76,872) $ (6,399)
[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/ Capital lease obligations 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.