Discontinued Operations (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 community	Dec. 31, 2013 community	Dec. 31, 2012 community
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities sold	4	3	2
Schedule of components from discontinued operations [Abstract]
Revenues		$ 4,454,000	$ 5,848,000
Property operating expenses		(1,406,000)	(2,181,000)
Depreciation and amortization		(1,098,000)	(1,513,000)
Expenses		(2,504,000)	(3,694,000)
Operating income from real estate sold		1,950,000	2,154,000
Gain on sale of real estate		29,223,000	10,870,000
Internal disposition costs		0	(1,087,000)
Income from discontinued operations	0	31,173,000	11,937,000
Linden Square [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Units in the community		183
Sales price of communities sold		25,300,000
Gain on sale of real estate		12,700,000
Cambridge [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Units in the community		40
Sales price of communities sold		4,700,000
Gain on sale of real estate		2,500,000
Brentwood [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Units in the community		140
Sales price of communities sold		27,500,000
Gain on sale of real estate		14,000,000
Tierra Del Sol/Norte and Alpine Country [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price of communities sold			28,300,000
Gain on sale of real estate			$ 10,900,000
Number of communities sold			2