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Unsecured Debt and Lines of Credit Debt Narrative (Details) (USD $)
 12 Months Ended 1 Months Ended 3 Months Ended
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Apr. 30, 2013
Sep. 30, 2012
Apr. 01, 2014
Sep. 30, 2013
Debt Instrument [Line Items]              
Unsecured debt   2,617,482,000us-gaap_UnsecuredDebt 1,410,023,000us-gaap_UnsecuredDebt        
Debt Instrument, Face Amount   1,900,000,000us-gaap_DebtInstrumentFaceAmount 600,000,000us-gaap_DebtInstrumentFaceAmount        
Basis spread on rate (in hundredths) 2.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1            
BRE Properties, Inc. [Member]              
Debt Instrument [Line Items]              
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt   1,747,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt
/ us-gaap_BusinessAcquisitionAxis
= ess_BrePropertiesIncMember		          
Unsecured Bonds 5.500% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount   300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds5.500Member		          
Unsecured Bonds 5.200% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount   300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds5.200Member		          
Unsecured Bonds 3.375% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount   300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.375Member		          
Unsecured Bonds 3.875% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount   400,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member		          
Unsecured Debt [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Unamortized Premium   27,500,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		 5,000,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		        
Fixed Rate Bond One [Member]              
Debt Instrument [Line Items]              
Unsecured debt   465,000,000us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= ess_FixedRateBondOneMember		 465,000,000us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= ess_FixedRateBondOneMember		        
Unsecured Bonds 4.5% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage   4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds45Member		 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds45Member		        
Maturity date   Sep. 30, 2017          
Debt Instrument, Interest Rate, Effective Percentage   4.50%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds45Member		 4.50%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds45Member		        
Loans Payable [Member]              
Debt Instrument [Line Items]              
Unsecured debt     350,000,000us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		        
Debt Instrument, Face Amount   225,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		 350,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		        
Long-term Debt, Weighted Average Interest Rate   2.40%us-gaap_LongtermDebtWeightedAverageInterestRate
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		 2.50%us-gaap_LongtermDebtWeightedAverageInterestRate
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		        
Basis spread on rate (in hundredths)   1.05%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		          
Term of loan   5 years          
Senior Notes [Member] | BRE Properties, Inc. [Member]              
Debt Instrument [Line Items]              
Unsecured debt   934,700,000us-gaap_UnsecuredDebt
/ us-gaap_BusinessAcquisitionAxis
= ess_BrePropertiesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt           900,000,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt
/ us-gaap_BusinessAcquisitionAxis
= ess_BrePropertiesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Senior Notes [Member] | Unsecured Bonds 5.500% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage   5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds5.500Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Notes [Member] | Unsecured Bonds 5.200% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage   5.20%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds5.200Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Notes [Member] | Unsecured Bonds 3.375% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage   3.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.375Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Notes [Member] | Unsecured Bonds 3.875% [Member]              
Debt Instrument [Line Items]              
Unsecured debt   397,200,000us-gaap_UnsecuredDebt
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Debt Instrument, Interest Rate, Stated Percentage   3.875%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		       3.875%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt Instrument, Face Amount           400,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt offering price           99.234%ess_DebtInstrumentDebtOfferingPricePercentageofParValue
/ us-gaap_DebtInstrumentAxis
= ess_UnsecuredBonds3.875Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Unsecured Bonds 3.25% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage       3.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds325Member		      
Proceeds from Issuance of Unsecured Debt       300,000,000.0us-gaap_ProceedsFromIssuanceOfUnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds325Member		      
Maturity date       May 01, 2023      
Debt offering price       99.152%ess_DebtInstrumentDebtOfferingPricePercentageofParValue
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds325Member		      
Long-term Debt, Gross   298,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds325Member		 297,700,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds325Member		        
Unsecured Bonds 3.625% [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Interest Rate, Stated Percentage             3.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds3625Member
Proceeds from Issuance of Unsecured Debt         300,000,000.0us-gaap_ProceedsFromIssuanceOfUnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds3625Member		    
Maturity date         Aug. 15, 2022    
Debt offering price         98.99%ess_DebtInstrumentDebtOfferingPricePercentageofParValue
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds3625Member		    
Long-term Debt, Gross   297,600,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds3625Member		 297,300,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= ess_UnsecuredBonds3625Member