Debt - Scheduled Principal Repayments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2019 (Remainder)	$ 217,523
2020	479,743
2021	174,345
2022	85,067
2023	412,305
Thereafter	241,791
Long-term debt and convertible notes payable	1,610,774	$ 1,560,333
Unamortized premium	728	753
Net unamortized debt issuance costs	(12,323)	(10,541)
Total Indebtedness	$ 1,599,179	$ 1,550,545

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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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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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