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Summary of Significant Accounting Policies - Compensation Costs (Including Bonuses and Benefits) Capitalized (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Construction in Progress [Line Items] |  |  |
Salaries including bonuses and benefits, capitalized during the period | $ 6,964 | $ 6,063 | $ 6,717
Development [Member] |  |  |
Construction in Progress [Line Items] |  |  |
Salaries including bonuses and benefits, capitalized during the period | 3,185 | 4,390 | 3,182
Redevelopment [Member] |  |  |
Construction in Progress [Line Items] |  |  |
Salaries including bonuses and benefits, capitalized during the period | 968 | 319 | 144
Tenant Improvements [Member] |  |  |
Construction in Progress [Line Items] |  |  |
Salaries including bonuses and benefits, capitalized during the period | $ 2,811 | $ 1,354 | $ 3,391

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