Real Estate Investments (Details) (USD $)	12 Months Ended				3 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended		12 Months Ended																																	3 Months Ended	12 Months Ended			12 Months Ended											3 Months Ended								12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2013 Unit Community Apartment Project	Dec. 31, 2012 Unit Community	Dec. 31, 2011	Dec. 31, 2013 Canada Pension Plan Investment Board (CPPIB) I [Member] Unit Project	Dec. 31, 2013 CPPIB Epic Phase I and II [Member] Unit	Dec. 31, 2013 Essex Apartment Value Fund II LP Fund II [Member]	Dec. 31, 2012 Essex Apartment Value Fund II LP Fund II [Member]	Dec. 31, 2013 Real Estate Under Development Activities [Member] Unit Project	Dec. 31, 2013 Real Estate predevelopment projects [Member] Unit Project	Aug. 31, 2013 Equity Method Investment [Member]	Dec. 31, 2013 Equity Method Investment [Member] Unit	Jun. 30, 2012 Equity Method Investment [Member]	Dec. 31, 2013 Equity Method Investment [Member] Wesco I LLC [Member] Unit	Dec. 31, 2013 Membership interest in Wesco I [Member]	Dec. 31, 2012 Membership interest in Wesco I [Member]	Dec. 31, 2013 Membership interest in Wesco III [Member]	Dec. 31, 2012 Membership interest in Wesco III [Member]	Dec. 31, 2013 Partnership interest in Fund II [Member]	Dec. 31, 2012 Partnership interest in Fund II [Member]	Dec. 31, 2013 Membership interest in a limited liability company that owns Expo [Member]	Dec. 31, 2012 Membership interest in a limited liability company that owns Expo [Member]	Dec. 31, 2013 Total operating co-investments [Member]	Dec. 31, 2012 Total operating co-investments [Member]	Dec. 31, 2013 Membership interests in limited liability companies with CPPIB that own and are developing Epic, Connolly Station, Mosso I & II, Park 20 and The Village [Member]	Dec. 31, 2012 Membership interests in limited liability companies with CPPIB that own and are developing Epic, Connolly Station, Mosso I & II, Park 20 and The Village [Member]	Dec. 31, 2013 Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]	Dec. 31, 2012 Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]	Dec. 31, 2013 Membership interests in limited liability companies that owns and is developing One South Market [Member]	Dec. 31, 2012 Membership interests in limited liability companies that owns and is developing One South Market [Member]	Dec. 31, 2013 Total development co-investments [Member]	Dec. 31, 2012 Total development co-investments [Member]	Dec. 31, 2013 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1% [Member]	Dec. 31, 2012 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1% [Member]	Dec. 31, 2013 Preferred interests in related party limited liability companies that owns Sage at Cupertino with a preferred return of 9.5% [Member]	Dec. 31, 2012 Preferred interests in related party limited liability companies that owns Sage at Cupertino with a preferred return of 9.5% [Member]	Dec. 31, 2013 Preferred interest in a related party limited liability company that owns Madison Park at Anaheim with a preferred return of 9% [Member]	Dec. 31, 2012 Preferred interest in a related party limited liability company that owns Madison Park at Anaheim with a preferred return of 9% [Member]	Dec. 31, 2013 Preferred interest in related party limited liability company that owns an apartment development in Redwood City with a preferred return of 12% [Member]	Dec. 31, 2012 Preferred interest in related party limited liability company that owns an apartment development in Redwood City with a preferred return of 12% [Member]	Dec. 31, 2013 Preferred interest in a limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]	Dec. 31, 2012 Preferred interest in a limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]	Dec. 31, 2013 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member]	Dec. 31, 2012 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member]	Dec. 31, 2013 Total preferred interest investments [Member]	Dec. 31, 2012 Total preferred interest investments [Member]	Mar. 31, 2013 Palo Alto, California [Member]	Dec. 31, 2012 Wesco I LLC [Member] Apartment	Dec. 31, 2013 Wesco I LLC [Member] Equity Method Investment [Member]	Dec. 31, 2012 Wesco I LLC [Member] Equity Method Investment [Member]	Dec. 31, 2013 Essex Apartment Value Fund II LP Fund II [Member] Community Property	Dec. 31, 2012 Essex Apartment Value Fund II LP Fund II [Member] Community	Dec. 31, 2013 Essex Apartment Value Fund II LP Fund II [Member] Equity Method Investment [Member] Apartment Investor	Dec. 31, 2013 Canada Pension Plan Investment Board (CPPIB) [Member] Apartment	Dec. 31, 2013 Canada Pension Plan Investment Board (CPPIB) [Member] Maximum [Member]	Dec. 31, 2013 Canada Pension Plan Investment Board (CPPIB) [Member] Minimum [Member]	Sep. 30, 2011 Fountain at La Brea [Member] Equity Method Investment [Member] Unit sqft	Dec. 31, 2011 Santa Monica at La Brea [Member] Equity Method Investment [Member] sqft Unit	May 31, 2013 Limited liability company that owns and is developing One South Market [Member] Unit	Dec. 31, 2011 Wesco II LLC [Member] Equity Method Investment [Member]	Jun. 30, 2011 Los Angeles I [Member] Equity Method Investment [Member]	Jun. 30, 2013 Los Angeles II [Member] Equity Method Investment [Member]	Mar. 31, 2013 Los Angeles II [Member] Equity Method Investment [Member] Apartment	Mar. 31, 2013 Redwood City, California [Member] Equity Method Investment [Member]	Sep. 30, 2013 Anaheim [Member]	Sep. 30, 2013 Anaheim [Member] Maximum [Member]	Sep. 30, 2013 Anaheim [Member] Minimum [Member]	Dec. 31, 2013 Wesco III [Member] Apartment	Dec. 31, 2013 Wesco III [Member] Equity Method Investment [Member]	Dec. 31, 2011 Cupertino California [Member]	Jun. 30, 2012 Cupertino California [Member] Equity Method Investment [Member]	Dec. 31, 2013 Total co investment [Member]	Dec. 31, 2012 Total co investment [Member]	Dec. 31, 2011 Total co investment [Member]
Schedule Of Equity Method Investments [Line Items]
Number of communities acquired	6	11
Gain from sale of real estate	$ 29,200,000	$ 10,900,000																																												$ 1,500,000				$ 146,700,000	$ 106,000,000																				$ 146,758,000	$ 106,016,000	$ 0
Number of communities sold	3	2																																																5	7
Sale of land held for future development																																														9,100,000
Number of units sold	363	264
Ownership interest in joint venture (in hundredths)																																																				28.20%		55.00%	50.00%			55.00%
Prepayment penalties on debt obligation																																																		200,000	2,300,000
Pro rata gain on sale of property of joint venture																																																		36,600,000	29,100,000
Number of properties expected to be sold in 2014																																																		2
Number of institutional investors in partnership																																																				8
Equity investment contributions by institutional investors																																																				265,900,000
Equity investment, contribution by Company																																																150,000,000				75,000,000				9,000,000	5,800,000										38,400,000
Debt ratio as leverage (in hundredths)																																																				55.00%															50.00%
Number of apartment communities owned	164																																														9					2	6									2					3
Ownership split in joint venture																																																	50/50								50/50											50/50
Total equity commitment from partners																																																	300,000,000																			120,000,000
Each partner's equity commitment																																																	150,000,000																			60,000,000
Co-investment	677,133,000	571,345,000										14,000,000		142,025,000	143,874,000	39,073,000	9,941,000	4,166,000	53,601,000	12,041,000	18,752,000	197,305,000	226,168,000	301,538,000	186,362,000	18,545,000	16,552,000	17,115,000	0	337,198,000	202,914,000	94,711,000	91,843,000	15,775,000	14,438,000	13,824,000	13,175,000	9,455,000	0	8,865,000	0	0	22,807,000	142,630,000	142,263,000														175,000,000	13,000,000		9,700,000	8,600,000
Preferred return on preferred equity investment (in hundredths)																																																																						9.50%
Percentage debt in joint venture (in hundredths)																																															50.00%																				50.00%
Number of units to be developed by joint venture																																																								187	184	312
Square footage of real estate property																																																								18,200	12,750
Ownership interest in joint venture by partner (in hundredths)																																																								50.00%
Preferred Equity Investment Additional funding, Maximum										8,500,000	14,000,000
Stated term of preferred equity investment										3 years
Redemption penalties due to the early redemption of preferred equity investments																																																														400,000
Redemption of preferred equity investments																																																													13,100,000
Gain from redemption penalties due to early redemption of preferred equity investments																																																													500,000
Maximum Term Extended (in years)																																																																1 year
Income related to the restructured investment																																																																400,000
Preferred Returns Maturity Date																																																															Jan. 31, 2016							May 31, 2016
Preferred return on preferred equity investment in first five years (in hundredths)										12.00%																																																					12.00%
Preferred return on preferred equity investment, thereafter (in hundredths)																																																																	13.00%	9.00%			9.50%
Balance sheets [Abstract]
Rental properties and real estate under development	50,430,000	66,851,000																																																																					1,953,328,000	1,745,147,000
Other assets																																																																							61,578,000	168,061,000
Total assets																																																																							2,014,906,000	1,913,208,000
Debt																																																																							667,641,000	820,895,000
Other liabilities	22,189,000	22,167,000																																																																					125,479,000	91,922,000
Equity																																																																							1,221,786,000	1,000,391,000
Total liabilities and partners' equity																																																																							2,014,906,000	1,913,208,000
Company's share of equity																																																																							677,133,000	571,345,000
Statements of operations [Abstract]
Property revenues																																																																							100,402,000	130,128,000	106,386,000
Property operating expenses																																																																							(37,518,000)	(55,990,000)	(43,066,000)
Net operating income																																																																							62,884,000	74,138,000	63,320,000
Gain on sale of real estate	29,200,000	10,900,000																																												1,500,000				146,700,000	106,000,000																				146,758,000	106,016,000	0
Interest expense	(104,600,000)	(100,244,000)	(91,694,000)																																																																				(24,155,000)	(34,959,000)	(27,843,000)
General and administrative	(25,601,000)	(23,307,000)	(20,694,000)																																																																				(5,344,000)	(3,697,000)	(1,748,000)
Depreciation and amortization	(11,924,000)	(11,644,000)	(11,474,000)																																																																				(36,831,000)	(47,917,000)	(44,412,000)
Net income (loss)																																																																							143,312,000	93,581,000	(10,683,000)
Company's share of net income (loss)																																																																							55,865,000	41,745,000	(467,000)
Business Combination, Separately Recognized Transactions [Line Items]
Cost of acquired entity	349,100,000	551,100,000									164,300,000		670,400,000
Number of units acquired	1,079	2,052		1,507	280			2,501	200		657		2,713
Purchase Price	349,100,000	551,100,000									164,300,000		670,400,000
Units	1,079	2,052		1,507	280			2,501	200		657		2,713
Sales price of real estate	57,500,000	28,300,000				320,400,000	413,000,000
Number of active development projects	11			6				8
Number of predevelopment projects Owned									1
Estimated cost of active development projects	145,100,000			695,200,000				1,100,000,000
Estimated costs to be expended	114,200,000			216,200,000				407,000,000
Remaining Estimated cost to be contributed by Company	$ 62,800,000			$ 118,900,000