Business Segments (Details Textuals) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Conventional Real Estate Operations [Member]
Business Segments (Textuals) [Abstract]
Number of owned real estate properties in segments	215
Number of units in owned real estate properties in segments	67,049
Capital additions related to segments	$ 58.9	$ 64.0
Affordable Real Estate Operations [Member]
Business Segments (Textuals) [Abstract]
Number of owned real estate properties in segments	205
Number of units in owned real estate properties in segments	24,406
Capital additions related to segments	$ 8.3	$ 15.9