Debt - Scheduled Principal Repayments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
2018 (Remainder)	$ 52,396
2019	207,952
2020	494,608
2021	113,012
2022	62,529
Thereafter	537,215
Long-term debt and convertible notes payable	1,467,712	$ 1,438,386
Unamortized fair market value of assumed debt	830	856
Net unamortized debt issuance costs	(13,259)	(14,833)
Total indebtedness	$ 1,455,283	$ 1,424,409

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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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