Summary of Critical and Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) community partnership shares	Dec. 31, 2014 USD ($) community shares	Dec. 31, 2013 USD ($)
Principles of Consolidation [Abstract]
Noncontrolling interest in Operating Partnership (in hundredths)	3.30%	3.30%
Number of DownREIT limited partnerships the company consolidates | partnership	19
Number of communities within the DownREIT partnership | community	11
Assets related to variable interest entities, net intercompany eliminations	$ 241,000,000	$ 235,100,000
Liabilities related to variable interest entities, net of intercompany eliminations	$ 206,700,000	$ 209,100,000
Redemption rights of limited partners issuance of common stock for partnership unit, conversion basis	one share per unit basis
Total DownREIT units outstanding (in shares) | shares	963,172	974,790
Redemption value of the variable interest entities	$ 230,600,000	$ 201,400,000
Redeemable noncontrolling interest	45,452,000	23,256,000
Noncontrolling interest in limited partnerships	$ 18,400,000	30,800,000
Redemption of limited partnership interest, shares issuable per unit | shares	1
Property, Plant and Equipment [Line Items]
Long-term debt	$ 2,215,077,000	2,234,317,000
Real Estate Rental Properties [Abstract]
Threshold useful life of assets for capitalization	1 year
Depreciable life of various categories of fixed assets [Abstract]
Acquired in-place lease value, net	$ 2,857,000	$ 47,748,000
Number of communities held-for-sale | community	2	1
Revenues and Gains on Sale of Real Estate [Abstract]
Lease terms, minimum	6 months
Lease terms, maximum	12 months
Cash Equivalents and Restricted Cash [Abstract]
Original maturities of highly liquid investments to be classified as cash equivalents, maximum	3 months
Marketable Securities [Abstract]
Maturity date of investments in mortgage backed securities, first	November 2019	November 2019
Maturity date of investments in mortgage backed securities, final	September 2020	September 2020
Available-for-sale Securities [Abstract]
Available for Sale - Carrying Value	$ 137,485,000	$ 117,240,000
Held-to-maturity Securities [Abstract]
Marketable securities, amortized cost	130,335,000	106,955,000
Marketable securities, gross unrealized gain	7,150,000	5,285,000
Marketable securities, carrying value	137,485,000	112,240,000
Other investments, amortized cost		5,000,000
Other investments, gross unrealized gain		0
Other investments, carrying value		5,000,000
Total marketable securities and other investments, amortized cost		111,955,000
Total marketable securities and other investments, gross unrealized gain		5,285,000
Total marketable securities and other investments, carrying value		117,240,000
Proceeds from sale of available-for-sale securities	3,300,000	8,800,000	$ 24,200,000
Gain on sale of available-for-sale securities	0	900,000	1,800,000
Sale of other investments	5,600,000	0	0
Gain on sale of other investments	600,000
Capitalization Policy [Abstract]
Capitalized internal costs related to development and redevelopment projects	10,900,000	10,400,000	$ 7,500,000
Fair Value of Financial Instruments [Abstract]
Fixed rate debt carrying amount	4,800,000,000	4,400,000,000
Fixed rate debt fair value	4,800,000,000	4,600,000,000
Variable rate debt, carrying amount	525,300,000	651,700,000
Variable rate debt fair value	527,600,000	656,300,000
Mortgage backed securities fair value	110,200,000	96,000,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	6,022,672,000
Stockholders' equity, ending balance	6,237,733,000	6,022,672,000
Essex Portfolio, L.P. [Member]
Principles of Consolidation [Abstract]
Redeemable noncontrolling interest	45,452,000	23,256,000
Depreciable life of various categories of fixed assets [Abstract]
Acquired in-place lease value, net	2,857,000	47,748,000
Available-for-sale Securities [Abstract]
Available for Sale - Carrying Value	$ 137,485,000	117,240,000
Computer Software and Equipment [Member] | Minimum [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	3 years
Computer Software and Equipment [Member] | Maximum [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	5 years
Interior Unit Improvements [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	5 years
Furniture, Fixtures And Equipment [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	5 years
Land Improvements and Certain Exterior Components of Real Property [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	10 years
Real Estate Structures [Member]
Depreciable life of various categories of fixed assets [Abstract]
Depreciable life, average	30 years
Investment-grade unsecured bonds [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	$ 11,618,000	9,435,000
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	68,000	145,000
Available for Sale - Carrying Value	11,686,000	9,580,000
Investment funds-US treasuries [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	3,675,000	3,769,000
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	(9,000)	3,000
Available for Sale - Carrying Value	3,666,000	3,772,000
Common Stock [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	34,655,000	25,755,000
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	7,091,000	5,137,000
Available for Sale - Carrying Value	41,746,000	30,892,000
Mortgage backed securities [Member]
Held-to-maturity Securities [Abstract]
Held to Maturity - Amortized Cost	80,387,000	67,996,000
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities	$ 80,387,000	$ 68,000,000
Common Stock [Member]
Status of cash dividends distributed [Abstract]
Ordinary income (in hundredths)	99.28%	70.03%	77.34%
Capital gains (in hundredths)	0.72%	21.95%	17.64%
Unrecaptured section 1250 capital gain (in hundredths)	0.00%	8.02%	5.02%
Total cash dividends distributed (in hundredths)	100.00%	100.00%	100.00%
Series G and H Preferred Stock [Member]
Status of cash dividends distributed [Abstract]
Ordinary income (in hundredths)	99.28%	70.03%	77.34%
Capital gains (in hundredths)	0.72%	21.95%	17.64%
Unrecaptured section 1250 capital gain (in hundredths)	0.00%	8.02%	5.02%
Total cash dividends distributed (in hundredths)	100.00%	100.00%	100.00%
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ (51,452,000)
Other comprehensive income before reclassification	1,411,000
Amounts reclassified from accumulated other comprehensive loss	8,030,000
Other comprehensive income	9,441,000
Stockholders' equity, ending balance	(42,011,000)	$ (51,452,000)
Accumulated Other Comprehensive Income (Loss) [Member] | Essex Portfolio, L.P. [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(49,356,000)
Other comprehensive income before reclassification	1,458,000
Amounts reclassified from accumulated other comprehensive loss	8,300,000
Other comprehensive income	9,758,000
Stockholders' equity, ending balance	(39,598,000)	(49,356,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(56,003,000)
Other comprehensive income before reclassification	(393,000)
Amounts reclassified from accumulated other comprehensive loss	8,030,000
Other comprehensive income	7,637,000
Stockholders' equity, ending balance	(48,366,000)	(56,003,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Essex Portfolio, L.P. [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(53,980,000)
Other comprehensive income before reclassification	(407,000)
Amounts reclassified from accumulated other comprehensive loss	8,300,000
Other comprehensive income	7,893,000
Stockholders' equity, ending balance	(46,087,000)	(53,980,000)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	4,551,000
Other comprehensive income before reclassification	1,804,000
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income	1,804,000
Stockholders' equity, ending balance	6,355,000	4,551,000
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Essex Portfolio, L.P. [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	4,624,000
Other comprehensive income before reclassification	1,865,000
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income	1,865,000
Stockholders' equity, ending balance	$ 6,489,000	4,624,000
Adjustments for New Accounting Principle, Early Adoption [Member]
Property, Plant and Equipment [Line Items]
Long-term debt		$ 29,400,000