Outstanding Loans and Security Agreements - Schedule of Repayments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-term Debt, Fiscal Year Maturity [Abstract]
2019	$ 29,878
2020	391,060
2021	153,639
2022	40,059
2023	44,209
Thereafter	127,650
Total	786,495	$ 1,008,104
Interest expense	$ 85,800	$ 108,600	$ 81,200

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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