Discontinued Operations (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Discontinued Operations [Abstract]
Number of communities sold	1		5
Number of units sold			353
Number of office building sold	1
Sales price of communities sold	$ 23,400,000		$ 38,000,000
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate	(8,382,000)	0	(8,626,000)
Schedule of components from discontinued operations [Abstract]
Revenues	1,016,000	2,447,000	4,498,000
Property operating expenses	(510,000)	(1,042,000)	(1,760,000)
Depreciation and amortization	(315,000)	(700,000)	(1,224,000)
Expenses	(825,000)	(1,742,000)	(2,984,000)
Operating income from real estate sold	191,000	705,000	1,514,000
Interest expense, secured mortgage debt	0	0	0
Gain on sale of real estate	8,382,000	0	8,626,000
Internal disposition costs	(839,000)	0	(683,000)
Income from discontinued operations	$ 7,734,000	$ 705,000	$ 9,457,000