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Equity Based Compensation Plans, Summary information of stock options outstanding (Details) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Number of options outstanding (in shares) 664,785us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions    
Options outstanding, Weighted-average remaining contractual life (years) 6 years 1 month 24 days    
Options outstanding, Weighted-average exercise price (in dollars per share) $ 138.78us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1    
Number of options exercisable (in shares) 395,986us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions    
Options exercisable, Weighted-average exercise price (in dollars per share) $ 133.99us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1    
Restricted Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock Issued During Period, Shares, New Issues 22,014us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember		 1,556us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember		 1,614us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Unrecognized compensation cost $ 3.5us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember		    
Unrecognized compensation cost, weighted average recognition period, minimum 1 year    
Unrecognized compensation cost, weighted average recognition period, maximum 7 years    
$62.34 - $101.01 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Exercise price range, lower range limit (in dollars per share) $ 66.05us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
Exercise price range, upper range limit (in dollars per share) $ 101.01us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
Number of options outstanding (in shares) 39,590us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
Options outstanding, Weighted-average remaining contractual life (years) 2 years 9 months 24 days    
Options outstanding, Weighted-average exercise price (in dollars per share) $ 79.64us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
Number of options exercisable (in shares) 39,590us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
Options exercisable, Weighted-average exercise price (in dollars per share) $ 79.64us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeOneMember		    
105.64 - 161.98 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Exercise price range, lower range limit (in dollars per share) $ 103.82us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
Exercise price range, upper range limit (in dollars per share) $ 161.98us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
Number of options outstanding (in shares) 561,626us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
Options outstanding, Weighted-average remaining contractual life (years) 6 years 1 month 24 days    
Options outstanding, Weighted-average exercise price (in dollars per share) $ 139.05us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
Number of options exercisable (in shares) 303,670us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
Options exercisable, Weighted-average exercise price (in dollars per share) $ 134.22us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeTwoMember		    
164.76 - 164.76 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Exercise price range, lower range limit (in dollars per share) $ 164.76us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember		    
Exercise price range, upper range limit (in dollars per share) $ 179.48us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember		    
Number of options outstanding (in shares) 63,569us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember		    
Options outstanding, Weighted-average remaining contractual life (years) 8 years 2 months 24 days    
Options outstanding, Weighted-average exercise price (in dollars per share) $ 173.22us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember		    
Number of options exercisable (in shares) 52,726us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember		    
Options exercisable, Weighted-average exercise price (in dollars per share) $ 173.49us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= ess_PriceRangeThreeMember