Debt - Scheduled Principal Repayments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2018	$ 94,400
2019	213,573
2020	576,379
2021	255,027
2022	98,840
Thereafter	200,167
Long-term debt and convertible notes payable	1,438,386	$ 1,505,671
Unamortized fair market value of assumed debt	856	1,336
Net unamortized debt issuance costs	(14,833)	(18,289)
Total indebtedness	$ 1,424,409	$ 1,488,718

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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 premium.

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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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