Investments in Real Estate Entities (Details) (USD $)	12 Months Ended																12 Months Ended				12 Months Ended		1 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2012 home	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Fund I loan item community option	Dec. 31, 2012 Fund I Avalon Lakeside	Dec. 31, 2012 Fund I Avalon Poplar Creek	Dec. 31, 2012 Fund I Avalon Lombard	Dec. 31, 2012 Fund I Avalon Paseo Place	Dec. 31, 2012 Fund I Avalon Skyway	Dec. 31, 2012 Fund I Avalon at Aberdeen Station	Dec. 31, 2012 Fund II investor loan	Dec. 31, 2012 Fund II Avalon Watchung home	Dec. 31, 2012 CVP I, LLC	Dec. 31, 2011 CVP I, LLC	Dec. 31, 2010 CVP I, LLC	Feb. 29, 2004 CVP I, LLC item	Dec. 31, 2012 MVP I, LLC	Dec. 31, 2011 MVP I, LLC	Dec. 31, 2010 MVP I, LLC	Dec. 31, 2004 MVP I, LLC item	Dec. 31, 2011 Aria at Hathorne Hill, LLC	Jun. 30, 2007 Aria at Hathorne Hill, LLC item	Feb. 29, 2012 4.61% fixed-rate mortgage note	Dec. 31, 2012 Variable rate bonds maturing in November 2036 CVP I, LLC	Dec. 31, 2012 6.02% fixed-rate mortgage note MVP I, LLC	Jul. 31, 2012 Avalon Del Rey home	Dec. 31, 2012 Arna Valley View LP home	Dec. 31, 2012 Arna Valley View LP Variable rate notes	Dec. 31, 2012 Arna Valley View LP Fixed rate notes	Jun. 30, 2012 Eaves Cerritos home	Feb. 29, 2012 The Mark Pasadena home	Dec. 31, 2012 Eaves Burlington home
Investment in Real Estate Entities
Number of apartment homes																361				313		64					101
Debt outstanding				$ 254,354,000							$ 490,078,000													$ 117,000,000	$ 105,000,000			$ 5,678,000	$ 5,963,000
Percentage of pro rate share of amount paid related to guaranteed obligations will reimburse by partner													80.00%
Number of extension options				2
Period of extension				1 year
Equity investment, net of distributions and excluding the purchase of mortgage note secured				21,121,000							107,938,000	63,000,000										23,621,000
Combined general partner and limited partner equity interest (as a percent)				15.20%							31.30%					20.00%				25.00%		50.00%					0.01%
Distributions percentage after achievement of a threshold return																50.00%
Percentage of apartment homes for which affordable rents are available with community																											100.00%
Debt interest rate																													4.00%
Percentage of homes built and sold																						30.00%
Impairment of investment in an unconsolidated joint venture		1,955,000
Acquisition of mortgage note																					1,700,000
Number of operating apartment communities sold				6
Proceeds from sale of real estate					20,500,000	27,200,000	35,450,000	30,900,000	90,000,000	66,250,000
Gain on sale of communities	106,195,000	22,246,000		7,971,000
Equity in income of unconsolidated entities	20,914,000	5,120,000	762,000	7,971,000									5,394,000	4,493,000	4,368,000		493,000	(626,000)	(881,000)
Number of loans secured by individual assets				13							14
Maximum amount that will be paid for capital contributions made by partners (as a percent)				10.00%							10.00%
Maximum amount that will be paid for capital contributions made by partners				7,500,000							8,910,000
Number of institutional investors				9							6
Number of apartment homes included in joint venture apartment communities owned	52,792																									309
Ownership interest acquired (as a percent)																										30.00%
Repayment of secured debt																										43,606,000
Acquisition of joint venture partner additional equity interest	3,350,000	9,070,000																								67,200,000
Ownership additional interest acquired (as a percent)																										70.00%
Promoted interest in unconsolidated equities																										4,055,000
Gain on acquisition of unconsolidated entity	14,194,000																									14,194,000
Number of apartment homes acquired												334																		151	84	203
Purchase price																														29,500,000	19,400,000	40,250,000
Mortgage notes assumed																							$ 11,958,000
Stated interest rate, percentage																							4.61%		6.02%