Long-Term Debt - Summary of scheduled principal repayments on long-term debt including capital lease obligations (Details 1) $ in Thousands  | 
 Dec. 31, 2017  
USD ($) 
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| Debt Disclosure [Abstract] | |
| 2018 | $ 619,373 | 
| 2019 | 626,334 | 
| 2020 | 622,129 | 
| 2021 | 2,571,257 | 
| 2022 | 431,674 | 
| Thereafter | 1,553,815 | 
| Total | $ 6,424,582 | 
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- References No definition available. 
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- Definition Amount of long-term debt and capital lease obligations including current maturities. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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- Definition Principal amount of long-term debt and capital lease obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. No definition available. 
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