Long-term Debt - Principal payments (Table) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Current portion of long-term bank loans	$ 153,930	$ 144,900
Long-term bank loans, net of current portion and unamortized loan issuance costs	930,217	938,699
Long-term Debt [Member]
Debt Instrument [Line Items]
June 30, 2022	153,930
June 30, 2023	162,204
June 30, 2024	346,208
June 30, 2025	147,703
June 30, 2026	199,155
June 30, 2027 and thereafter	85,736
Total Long-term bank loans	1,094,936
Unamortized loan issuance costs	(10,789)	$ (13,761)
Total Long-term bank loans, net	1,084,147
Current portion of long-term bank loans	153,930
Long-term bank loans, net of current portion and unamortized loan issuance costs	$ 930,217

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Carrying value as of the balance sheet date of current portion of long-term loans payable to bank due within one year or the operating cycle if longer.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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