Investments - Schedule of Net Aggregate Amortization Expense of Intangible Assets and Liabilities (Details) $ in Thousands |
Dec. 31, 2017
USD ($)
|
|---|---|
| Investments in and Advances to Affiliates, Schedule of Investments [Abstract] | |
| Amortization in 2018 | $ 32,343 |
| Amortization in 2019 | 30,736 |
| Amortization in 2020 | 28,717 |
| Amortization in 2021 | 26,108 |
| Amortization in 2022 | 22,838 |
| Amortization thereafter | 113,858 |
| Total future minimum amortization | $ 254,600 |