Summary of Critical and Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 community partnership	Dec. 31, 2013	Dec. 31, 2012
Principles of Consolidation [Abstract]
Noncontrolling interest in Operating Partnership (in hundredths)	3.30%	5.40%
Number of DownREIT limited partnerships the company consolidates	17
Number of communities within the DownREIT partnership	10
Assets related to variable interest entities, net intercompany eliminations	$ 200,000,000	$ 194,900,000
Liabilities related to variable interest entities, net of intercompany eliminations	196,600,000	178,300,000
Redemption rights of limited partners issuance of common stock for partnership unit, conversion basis	one share per unit basis
Common Stock, Redemption Of Limited Partnership Interest, Shares Issuable Per Unit	1
Total DownREIT units outstanding (in shares)	941,138	1,007,879
Redemption value of the variable interest entities	194,000,000	145,000,000
Real Estate Rental Properties [Abstract]
Threshold useful life of assets for capitalization	1 year
Depreciable life of various categories of fixed assets [Abstract]
Expected lease term of acquired tenant	20 months
Proceeds from Sale of Available-for-sale Securities	8,753,000	24,172,000	61,703,000
Available-for-sale Securities, Gross Realized Gain (Loss)	886,000	1,767,000	819,000
Acquired in-place lease value	47,747,000	4,513,000
Revenues and Gains on Sale of Real Estate [Abstract]
Lease terms, minimum	6 months
Lease terms, maximum	12 months
No rent time period, minimum	1 month
No rent time period, maximum	2 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
Proceeds from Sale of Available-for-sale Securities	8,753,000	24,172,000	61,703,000
Available-for-sale Securities, Gross Realized Gain (Loss)	886,000	1,767,000	819,000
Capitalization Policy [Abstract]
Capitalized internal costs related to development and redevelopment projects	10,400,000	7,500,000	6,200,000
Fair Value of Financial Instruments [Abstract]
Fixed rate debt carrying amount	4,400,000,000	2,300,000,000
Fixed rate debt fair value	4,600,000,000	2,300,000,000
Variable rate debt, carrying amount	660,600,000	737,000,000
Variable rate debt fair value	656,300,000	719,400,000
Mortgage backed securities fair value	96,000,000	86,200,000
Available-for-sale Securities [Abstract]
Available for Sale - Carrying Value	117,240,000	90,084,000
Held-to-maturity Securities [Abstract]
Total Amortized Cost	106,955,000	90,876,000
Total Gross Unrealized Gain (Loss)	5,285,000	(792,000)
Total Fair Value	112,240,000	90,084,000
Available-for-sale Securities and Held-to-maturity Securities	111,955,000
Available-For-Sale Securities And Held-To-Maturity Securities, Unrealized Holding Gain (Loss)	5,285,000
Change in fair value and amortization of derivatives
Balance at beginning	(59,724,000)
Balance at the end	(56,003,000)	(59,724,000)
Unrealized gains/(losses) on available for sale securities [Abstract]
Balance at beginning	(748,000)
Changes in fair value of marketable securities	6,302,000	(1,556,000)	1,411,000
Balance at the end	4,551,000	(748,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassification	6,898,000
Amounts reclassified from accumulated other comprehensive loss	2,122,000
Net other comprehensive income (loss)	9,020,000
Balance at the end	(51,452,000)	(60,472,000)
Accumulated Other Comprehensive Income (Loss) [Member]
Change in fair value and amortization of derivatives
Other comprehensive income before reclassification	758,000
Amounts reclassified from accumulated other comprehensive loss	2,963,000
Net other comprehensive income	3,721,000
Unrealized gains/(losses) on available for sale securities [Abstract]
Changes in fair value of marketable securities	6,140,000	(1,472,000)	1,345,000
Amounts reclassified from accumulated other comprehensive loss	(841,000)
Net other comprehensive income (loss)	5,299,000
Investment-grade unsecured bonds [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	9,435,000	15,446,000
Available for Sale - Gross Unrealized Gain (Loss)	145,000	509,000
Available for Sale - Carrying Value	9,580,000	15,955,000
Investment funds-US treasuries [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	3,769,000	3,675,000
Available for Sale - Gross Unrealized Gain (Loss)	3,000	3,000
Available for Sale - Carrying Value	3,772,000	3,678,000
Common Stock [Member]
Available-for-sale Securities [Abstract]
Available for Sale - Amortized Cost	25,755,000	13,104,000
Available for Sale - Gross Unrealized Gain (Loss)	5,137,000	(1,304,000)
Available for Sale - Carrying Value	30,892,000	11,800,000
Mortgage backed securities [Member]
Held-to-maturity Securities [Abstract]
Held to Maturity - Amortized Cost	67,996,000	58,651,000
Held to Maturity - Gross Unrealized Gain (Loss)	0	0
Held-to-maturity Securities	67,996,000	58,651,000
Other Investments [Member]
Held-to-maturity Securities [Abstract]
Held to Maturity - Amortized Cost	5,000,000
Held to Maturity - Gross Unrealized Gain (Loss)	0
Held-to-maturity Securities	5,000,000
Common Stock [Member]
Status of cash dividends distributed [Abstract]
Ordinary income (in hundredths)	70.03%	77.34%	70.58%
Capital gains (in hundredths)	21.95%	17.64%	8.75%
Unrecaptured section 1250 capital gain (in hundredths)	8.02%	5.02%	7.97%
Return of capital (in hundredths)	0.00%	0.00%	12.70%
Total cash dividends distributed (in hundredths)	100.00%	100.00%	100.00%
Series F, G and H Preferred Stock [Member]
Status of cash dividends distributed [Abstract]
Ordinary income (in hundredths)	70.03%	77.34%	80.85%
Capital gains (in hundredths)	21.95%	17.64%	10.02%
Unrecaptured section 1250 capital gain (in hundredths)	8.02%	5.02%	9.13%
Total cash dividends distributed (in hundredths)	100.00%	100.00%	100.00%
Essex Portfolio, L.P. [Member]
Depreciable life of various categories of fixed assets [Abstract]
Proceeds from Sale of Available-for-sale Securities	8,753,000	24,172,000	61,703,000
Available-for-sale Securities, Gross Realized Gain (Loss)	886,000	1,767,000	819,000
Acquired in-place lease value	47,747,000	4,513,000
Marketable Securities [Abstract]
Proceeds from Sale of Available-for-sale Securities	8,753,000	24,172,000	61,703,000
Available-for-sale Securities, Gross Realized Gain (Loss)	886,000	1,767,000	819,000
Available-for-sale Securities [Abstract]
Available for Sale - Carrying Value	117,240,000	90,084,000
Change in fair value and amortization of derivatives
Balance at beginning	(58,148,000)
Balance at the end	(53,980,000)	(58,148,000)
Unrealized gains/(losses) on available for sale securities [Abstract]
Balance at beginning	(792,000)
Changes in fair value of marketable securities	6,302,000	(1,556,000)	1,411,000
Balance at the end	4,624,000	(792,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassification	7,507,000
Amounts reclassified from accumulated other comprehensive loss	2,077,000
Net other comprehensive income (loss)	9,584,000
Balance at the end	(49,356,000)	(58,940,000)
Essex Portfolio, L.P. [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Change in fair value and amortization of derivatives
Other comprehensive income before reclassification	1,205,000
Amounts reclassified from accumulated other comprehensive loss	2,963,000
Net other comprehensive income	4,168,000
Unrealized gains/(losses) on available for sale securities [Abstract]
Changes in fair value of marketable securities	6,302,000
Amounts reclassified from accumulated other comprehensive loss	(886,000)
Net other comprehensive income (loss)	$ 5,416,000
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