Outstanding Loans and Security Agreements - Schedule of Repayments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Remaining 2018	$ 19,322		$ 19,322
2019	241,136		241,136
2020	389,909		389,909
2021	153,639		153,639
2022	40,059		40,059
Thereafter	172,212		172,212
Total	1,016,277		1,016,277		$ 1,008,104
Interest expense	$ 26,167	$ 25,554	$ 49,204	$ 49,917

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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