Summary of Significant Accounting Policies - Construction-in-Progress (Textual) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 6,964	$ 6,063	$ 6,717
Development [Member]
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	3,185	4,390	3,182
Capitalized interest	$ 3,600	$ 3,100	$ 10,900