Organization and Basis of Presentation (Details) (USD $)	3 Months Ended
	Mar. 31, 2014 Project Unit Apartment Partnership Community Building		Mar. 31, 2013		Dec. 31, 2013
Schedule of Mergers [Line Items]
Share price (in dollars per share)	$ 174
Change in fair value and amortization of derivatives [Abstract]
Balance at beginning	$ (59,724,000)
Other comprehensive income (loss) before reclassification, derivative	472,000
Amounts reclassified from accumulated other comprehensive loss	2,093,000
Net other comprehensive income (loss)	2,565,000
Balance at the end	(57,159,000)
Unrealized gains/(losses) on available for sale securities [Abstract]
Balance at beginning	764,000				(748,000)
Other comprehensive income (loss) before reclassification, available for sale securities, total	1,914,000
Amounts reclassified from accumulated other comprehensive loss	(402,000)
Net other comprehensive income (loss)	1,512,000
Balance at the end	764,000				(748,000)
Accumulated other comprehensive loss, net by component [Abstract]
Balance at beginning	(56,395,000)				(60,472,000)
Other comprehensive income (loss) before reclassification	2,386,000
Amounts reclassified from accumulated other comprehensive loss	1,691,000
Net other comprehensive income (loss)	4,077,000
Balance at the end	(56,395,000)				(60,472,000)
Pro Forma results in connection with BRE merger
General partner ownership interest (in hundredths)	94.50%
Operating Partnership units outstanding (in shares)	2,176,222				2,149,802
Redemption value of Operating Partnership units outstanding	370,100,000				308,500,000
Number of apartment communities owned	176
Apartment units owned (in units)	37,569
Ownership interests, number of commercial buildings	4
Ownership interests, number of active development projects	13
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	99,537,000				90,876,000
Total Gross Unrealized Gain (Loss)	811,000				(792,000)
Total Carrying Value	100,348,000				90,084,000
Proceeds from sales of available for sale securities	4,000,000		20,300,000
Gain from sales of available-for-sale securities	400,000		1,800,000
Variable Interest Entities [Abstract]
Number of DownREIT limited partnerships the company consolidates	19
Number of communities within the DownREIT partnership	12
Total DownREIT Partnership's Outstanding units (shares)	1,007,879				1,007,879
Redemption value of the variable interest entities	171,400,000				144,600,000
Assets related to variable interest entities, net intercompany eliminations	233,400,000				194,900,000
Liabilities related to variable interest entities, net of intercompany eliminations	218,900,000				178,300,000
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,233,000		1,132,000
Fair Value of Financial Instruments [Abstract]
Fixed rate debt carrying amount	2,290,000,000
Fixed rate debt fair value	2,420,000,000
Variable rate debt, carrying amount	527,600,000
Variable rate debt fair value	500,000,000
Mortgage backed securities carrying value	60,600,000				58,700,000
Mortgage backed securities fair value	89,400,000				86,200,000
Capitalization Policy [Abstract]
Capitalized internal costs related to development and redevelopment projects	1,700,000		1,600,000
Capitalized salaries	900,000		600,000
Vista Capri [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Units in the community	106
Sales price of communities sold	14,400,000
Gain on sale of real estate	7,900,000
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	600,000		600,000
Intrinsic value of options exercised	600,000		900,000
Intrinsic value of the options outstanding and fully vested	21,100,000
Unrecognized compensation cost	6,100,000
Unrecognized compensation cost, weighted average recognition period, minimum	1 year
Unrecognized compensation cost, weighted average recognition period, maximum	5 years
Restricted Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	600,000		600,000
Unrecognized compensation cost	6,100,000
Unrecognized compensation cost, weighted average recognition period, minimum	1 year
Unrecognized compensation cost, weighted average recognition period, maximum	7 years
2014 LTIP Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Granted (in shares)	50,500
Percentage subject to performance based vesting (in hundredths)	90.00%
Percentage subject to service-based vesting (in hundredths)	10.00%
Percentage of performance based vesting of 2014 Ltip Units eligible to be earned on absolute total stockholders return (in hundredths)	0.33%
Percentage of performance based vesting of 2014 Ltip Units eligible to be earned on relative total stockholders return (in hundredths)	0.66%
Performance period	1 year
Long Term Incentive Plans - Z-1 Units and 2014 LTIP Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	600,000		500,000
Intrinsic value of the options outstanding and fully vested	22,400,000
Unrecognized compensation cost	7,700,000
Unamortized cost recognition period	6 years
Investment-Grade Unsecured Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	11,772,000				15,446,000
Gross Unrealized Gain (Loss)	96,000				509,000
Carrying Value	11,868,000				15,955,000
Investment Funds - US Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	5,017,000				3,675,000
Gross Unrealized Gain (Loss)	5,000				3,000
Carrying Value	5,022,000				3,678,000
Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	22,103,000				13,104,000
Gross Unrealized Gain (Loss)	710,000				(1,304,000)
Carrying Value	22,813,000				11,800,000
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	60,645,000				58,651,000
Gross Unrealized Gain (Loss)	0				0
Carrying Value	60,645,000				58,651,000
Essex Portfolio, L.P. [Member]
Change in fair value and amortization of derivatives [Abstract]
Balance at beginning	(58,148,000)
Other comprehensive income (loss) before reclassification, derivative	627,000
Amounts reclassified from accumulated other comprehensive loss	2,093,000
Net other comprehensive income (loss)	2,720,000
Balance at the end	(55,428,000)
Unrealized gains/(losses) on available for sale securities [Abstract]
Balance at beginning	811,000				(792,000)
Other comprehensive income (loss) before reclassification, available for sale securities, total	2,030,000
Amounts reclassified from accumulated other comprehensive loss	(427,000)
Net other comprehensive income (loss)	1,603,000
Balance at the end	811,000				(792,000)
Accumulated other comprehensive loss, net by component [Abstract]
Balance at beginning	(54,617,000)				(58,940,000)
Other comprehensive income (loss) before reclassification	2,657,000
Amounts reclassified from accumulated other comprehensive loss	1,666,000
Net other comprehensive income (loss)	4,323,000
Balance at the end	(54,617,000)				(58,940,000)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,233,000		1,132,000
BRE Properties, Inc. [Member]
Schedule of Mergers [Line Items]
Common shares conversion ratio in connection with merger (in shares)	0.2971
Cash consideration per share (in dollars per share)	$ 7.18
Special dividend (in dollars per share)	$ 5.15
Cash consideration before special dividend (in dollars per share)	$ 12.33
Number of shares of common stock issued in merger (in shares)	23,100,000
Share price (in dollars per share)	$ 61
Number of properties contributed	14
Value of properties contributed	1,400,000,000
Number of operating partnership units issued for properties contributed	8,600,000
Business Acquisition, Purchase Price Allocation [Abstract]
Rental properties, excluding co-investments	5,808,000,000
Co-investments	206,000,000
In-place lease value	97,000,000
Other Assets	96,000,000
Secured and unsecured debt	(1,736,000,000)
Other liabilities	(129,000,000)
Total consideration	4,342,000,000
Pro Forma results in connection with BRE merger
Total revenue	247,801,000		228,721,000
Net income available to common shareholders	129,385,000	[1],[2]	(12,956,000)	[1],[2]
Earnings per share, diluted (in dollars per share)	$ 2.12	[1]	$ (0.22)	[1]
Merger related costs	16,059,000		29,000,000
Income from discontinued operations	105,000,000
Number of BRE properties sold	3
BRE Properties, Inc. [Member] | Prepaid Expenses and Other Assets [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Acquired in-place lease value	19,000,000
BRE Properties, Inc. [Member] | Essex Portfolio, L.P. [Member]
Pro Forma results in connection with BRE merger
Total revenue	247,801,000		228,721,000
Net income available to common shareholders	$ 130,802,000	[1],[2]	$ (11,455,000)	[1],[2]
Earnings per share, diluted (in dollars per share)	$ 2.07	[1]	$ (0.18)	[1]

[1] 2014 supplemental pro forma net income available to common stockholders were adjusted to exclude $16,059 of merger related costs incurred by Essex during the three-months ended March 31, 2014. 2013 supplemental pro forma net income available to common stockholders were adjusted to include these charges plus an additional approximately $29,000 of merger expenses estimated to be incurred by Essex . 2014 and 2013 supplemental proforma earnings per share, diluted, were adjusted accordingly.

[2] 2014 supplemental pro forma net income available to common stockholders includes approximately $105 million from discontinued operations related to the sale of three BRE properties that are non-recurring transactions.