| Schedule of long-term debt | Long-term debt consisted of the following:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Interest Rate |  |  |  | Balance |  
|  |  | December 31,  |  | Maturities |  | December 31,  |  
|  |      | 2019 |      | 2018 |      | Through |      | 2019 |      | 2018 |  
|  |  |  |  |  |  |  |  | (in thousands) |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| $875.0 million senior secured revolving credit facility |  |  — |  |  3.96 | %   | 2024 |  | $ |  — |  | $ |  130,000 |  
| $75.0 million revolving credit line |  |  2.75 | %   |  — |  | 2020 |  |  |  75,000 |  |  |  — |  
| Term Loan A |  |  3.06 | %   |  4.01 | %   | 2024 |  |   |  1,565,512 |  |   |  1,256,167 |  
| $375.0 million Term Loan B (1) |  |  — |  |  4.26 | %   | 2021 |  |   |  — |  |   |  368,982 |  
| $700.0 million 4.750% senior unsecured notes |  |  — |  |  4.75 | %   | 2021 |  |   |  — |  |   |  561,021 |  
| $565.0 million 3.625% senior unsecured notes |  |  3.63 | %   |  — |  | 2024 |  |  |  558,781 |  |  |  — |  
| €662.9 million Norwegian Epic term loan (2) |  |  — |  |  4.58 | %   | 2022 |  |   |  — |  |   |  259,394 |  
| $260 million Norwegian Jewel term loan |  |  2.54 | %   |  — |  | 2022 |  |  |  221,860 |  |  |  — |  
| $230 million Pride of America term loan |  |  2.81 | %   |  — |  | 2021 |  |   |  229,621 |  |   |  — |  
| €529.8 million Breakaway one loan (2) |  |  2.84 | %   |  4.09 | %   | 2025 |  |   |  305,969 |  |   |  360,680 |  
| €529.8 million Breakaway two loan (2) |  |  4.10 | %   |  4.50 | %   | 2026 |  |   |  370,531 |  |   |  426,503 |  
| €590.5 million Breakaway three loan (2) |  |  2.98 | %   |  2.98 | %   | 2027 |  |   |  478,665 |  |   |  537,223 |  
| €729.9 million Breakaway four loan (2) |  |  2.98 | %   |  2.98 | %   | 2029 |  |   |  630,088 |  |   |  694,536 |  
| €710.8 million Seahawk 1 term loan (2) |  |  3.92 | %   |  3.92 | %   | 2030 |  |   |  692,150 |  |   |  756,061 |  
| €748.7 million Seahawk 2 term loan (2) |  |  3.92 | %   |  3.92 | %   | 2031 |  |   |  856,188 |  |   |  187,612 |  
| Leonardo newbuild one loan |  |  2.68 | %   |  2.68 | %   | 2034 |  |   |  48,009 |  |   |  48,009 |  
| Leonardo newbuild two loan |  |  2.77 | %   |  2.77 | %   | 2035 |  |   |  48,009 |  |   |  48,009 |  
| Leonardo newbuild three loan |  |  1.22 | %   |  1.22 | %   | 2036 |  |   |  42,700 |  |   |  43,667 |  
| Leonardo newbuild four loan |  |  1.31 | %   |  1.31 | %   | 2037 |  |   |  42,700 |  |   |  43,667 |  
| Sirena loan |  |  — |  |  2.75 | %   | 2019 |  |   |  — |  |   |  13,856 |  
| Explorer newbuild loan |  |  3.43 | %   |  3.43 | %   | 2028 |  |   |  242,449 |  |   |  268,970 |  
| Marina newbuild loan (3) |  |  2.75 | %   |  3.07 | %   | 2023 |  |   |  156,319 |  |   |  201,007 |  
| Riviera newbuild loan (4) |  |  2.48 | %   |  3.32 | %   | 2024 |  |   |  202,233 |  |   |  247,203 |  
| Finance lease and license obligations |  | Various |   | Various |   | 2028 |  |   |  34,909 |  |   |  39,524 |  
| Total debt |  |  |  |  |   |    |  |  |  6,801,693 |   |  |  6,492,091 |  
| Less: current portion of long-term debt |  |  |  |  |   |    |  |  |  (746,358) |   |  |  (681,218) |  
| Total long-term debt |  |  |  |  |   |    |  | $ |  6,055,335 |  | $ |  5,810,873 |  
| (1) | Includes original issue discount of $0.7 million as of December 31, 2018. | 
 
| (2) | Currently U.S. dollar-denominated. | 
 
| (3) | Includes premium of $0.1 million as of December 31, 2019 and 2018. | 
 
| (4) | Includes premium of $0.1 million and $0.2 million as of December 31, 2019 and 2018, respectively. | 
 | 
| Schedule of principal repayments on long-term debt including finance lease obligations | The following are scheduled principal repayments on long-term debt including finance lease obligations as of December 31, 2019 for each of the next five years (in thousands):  
|  |  |  |  |  
| Year |      | Amount |  
| 2020 |  | $ |  746,358 |  
| 2021 |  |   |  899,206 |  
| 2022 |  |   |  667,456 |  
| 2023 |  |   |  574,492 |  
| 2024 |  |   |  2,260,295 |  
| Thereafter |  |   |  1,778,870 |  
| Total |  | $ |  6,926,677 |  |