Debt - Aggregate Principal Repayments on Mortgage Notes (Details) - Mortgages [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
October 1, 2018 - December 31, 2018	$ 2,437
2019	177,317
2020	265,183
2021	352,767
2022	314,898
Thereafter	817,005
Total	$ 1,929,607	$ 2,071,038

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 of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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