Co-Investments (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	$ 197,364		$ 197,364		$ 107,840
Rental properties and real estate under development	993,258		993,258		750,808
Other assets	36,419		36,419		15,864
Total assets	1,029,677		1,029,677		766,672
Mortgage notes	598,435		598,435		450,693
Other liabilities	20,773		20,773		7,076
Equity	410,469		410,469		308,903
Total liabilities and equity	1,026,587		1,026,587		766,672
Company's share of equity	196,725		196,725		107,201
Property revenues	24,084	12,482	42,596	24,810
Property operating expenses	(9,719)	(5,533)	(17,695)	(10,662)
Net property operating income	14,365	6,949	24,901	14,148
Interest expense	(10,549)	(2,950)	(15,410)	(5,911)
General and administrative	(38)	0	(1,022)	0
Depreciation and amortization	(6,165)	(4,756)	(18,006)	(9,209)
Net loss	(8,030)	(757)	(9,537)	(972)
Company's share of net income (loss)	726	(360)	(647)	(401)
Equity Method Investment [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	196,725		196,725		107,201
Equity Method Investment [Member] | Apartment communities in downtown Los Angeles [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	22,767		22,767		0
Equity Method Investment [Member] | Limited partnership interest in Essex Apartment Value Fund II LP [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	65,532		65,532		66,000
Equity Method Investment [Member] | Wesco I LLC [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	(87)		(87)		0
Equity Method Investment [Member] | Cadence [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	52,407		52,407		0
Equity Method Investment [Member] | Essex Skyline at MacArthur Place [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	26,758		26,758		29,187
Equity Method Investment [Member] | Queen Anne [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	17,000		17,000		0
Equity Method Investment [Member] | Madison Park at Anaheim [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	12,348		12,348		12,014
Cost Method Investment [Member] | Series A Preferred Stock interest in Multifamily Technology Solutions Inc [Member]
Schedule Of Equity And Cost Method Investments [Line Items]
Co-investment	$ 639		$ 639		$ 639