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Commitments and Contingencies - Narrative (Details) | May 25, 2017 USD ($) | Sep. 30, 2018 USD ($) Property | Dec. 31, 2017 USD ($) | Aug. 31, 2010 USD ($)
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Capital Leases |  |  |  |
Capital lease term | 99 years |  |  |
Purchase option | $ 1 |  |  |
Capital lease obligation | $ 16,100,000 | $ 660,000 | $ 15,853,000 |
Minimum rental payments due in 2020 |  | $ 660,000 |  |
Environmental Indemnity Agreement |  |  |  |
Number of properties which were provided environmental indemnifications | Property |  | 3 |  |
Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement |  | $ 19,000,000 |  |
Development and Redevelopment Obligations |  |  |  |
Capital Leases |  |  |  |
Purchase obligations |  | 163,100,000 |  |
Capital Expenditures For Operating Properties |  |  |  |
Capital Leases |  |  |  |
Purchase obligations |  | 39,700,000 |  |
Third Party Construction |  |  |  |
Capital Leases |  |  |  |
Purchase obligations |  | 3,600,000 |  |
Other Obligations |  |  |  |
Capital Leases |  |  |  |
Purchase obligations |  | $ 2,100,000 |  |
Specialty Tax Guarantee | Anne Arundel County, Maryland | Tax Incremental Financing Bond |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loan amount |  |  |  | $ 30,000,000

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