Business of Organization - Additional Information (Details) - property	Sep. 30, 2018	Dec. 31, 2017
Business And Organization [Line Items]
Percentage of Operating Partnership held	74.30%	72.00%
Operating Property
Business And Organization [Line Items]
Number of real estate properties	50
Development Property
Business And Organization [Line Items]
Number of real estate properties	10
General Partner
Business And Organization [Line Items]
Percentage of Operating Partnership held	0.10%