Outstanding Loans and Security Agreements - Schedule of Repayments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Remainder of 2018	$ 5,052		$ 5,052
2019	29,523		29,523
2020	392,229		392,229
2021	153,639		153,639
2022	40,059		40,059
Thereafter	172,211		172,211
Total	792,713		792,713		$ 1,008,104
Interest expense	$ 18,800	$ 28,900	$ 68,000	$ 78,800

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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