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Summary of Significant Accounting Policies - Compensation Costs (Including Bonuses and Benefits) Capitalized (Details) - USD ($) $ in Thousands	12 Months Ended
	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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