Acquisition, Development, Construction and Disposition Activity Acquisition, Development, Construction and Disposition Activity (Schedule of Business Acquisitions) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 Units
Business Acquisition [Line Items]
Apartment units owned	13,676
Acquisition cost	$ 80,200,000
Alpha Mill Apartments Phase I [Member]
Business Acquisition [Line Items]
Apartment units owned	167
Acquisition cost	27,220
Alpha Mill Apartments Phase II [Member]
Business Acquisition [Line Items]
Apartment units owned	100
Acquisition cost	18,050
1160 Hammond [Member]
Business Acquisition [Line Items]
Apartment units owned	345
Acquisition cost	80,350
Varela [Member]
Business Acquisition [Line Items]
Apartment units owned	350
Acquisition cost	79,450
NorthwoodRavinPortfolio [Member]
Business Acquisition [Line Items]
Apartment units owned	962
Acquisition cost	323,900,000
Remaining payments to acquire	$ 205,070