Business Segments (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Business Segments (Textual) [Abstract]
Number of reportable segments	2
Conventional Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Capital additions related to segments	$ 86.6	$ 64.6
Affordable Real Estate Operations [Member]
Business Segments (Textual) [Abstract]
Capital additions related to segments	$ 1.7	$ 2.0
Conventional Real Estate [Member]
Business Segments (Textual) [Abstract]
Number of owned apartment communities in segments	161
Number of apartment homes in owned apartment communities in segments	49,314
Affordable Real Estate [Member]
Business Segments (Textual) [Abstract]
Number of owned apartment communities in segments	72
Number of apartment homes in owned apartment communities in segments	9,680