Business Segments (Details Textual) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) Segment Units Property	Mar. 31, 2015 USD ($)
Business Segments (Textual) [Abstract]
Number of reportable segments | Segment	2
Conventional Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Number of owned apartment communities in segments | Property	139
Number of apartment homes in apartment communities | Units	40,376
Affordable Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Number of owned apartment communities in segments | Property	56
Number of apartment homes in apartment communities | Units	8,685
Operating Segments [Member] | Conventional Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Capital additions related to segments | $	$ 70.0	$ 61.3
Operating Segments [Member] | Affordable Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Capital additions related to segments | $	$ 2.1	$ 2.6