Real Estate (Purchase Prices Allocated to Real Estate Assets and Liabilities) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Real Estate Properties [Line Items]
Purchase Price	$ 30,902,000
Christina Crossing [Member]
Real Estate Properties [Line Items]
Location	Wilmington, DE
Date Acquired	Feb. 22, 2017
Purchase Price	$ 27,902,000
Parcel adjacent to South Philadelphia Shopping Center [Member]
Real Estate Properties [Line Items]
Location	Philadelphia, PA
Date Acquired	Jul. 06, 2017
Purchase Price	$ 3,000,000