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Warrants (Details) (USD $)
3 Months Ended 12 Months Ended
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Sep. 30, 2012
Nov. 30, 2012
Jul. 02, 2013
Jun. 30, 2014
Warrants                  
(Loss)/gain recognized for change in the fair value of the warrant liability $ (2,545,000)us-gaap_FairValueAdjustmentOfWarrants $ (42,000)us-gaap_FairValueAdjustmentOfWarrants $ (2,587,000)us-gaap_FairValueAdjustmentOfWarrants $ 32,000us-gaap_FairValueAdjustmentOfWarrants          
Warrant                  
Warrants                  
Exercise price (in dollars per share)         $ 7.23us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
       
Number of shares of common stock to be purchased against outstanding warrants         285,920us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
       
Warrant | Total | Short term convertible notes issued September 2012                  
Warrants                  
Estimated fair value           100,000us-gaap_WarrantsAndRightsOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_DebtInstrumentAxis
= espr_ShortTermConvertibleNotesIssuedSeptember2012Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
     
Warrant | Total | Short term convertible notes issued November 2012                  
Warrants                  
Estimated fair value             200,000us-gaap_WarrantsAndRightsOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_DebtInstrumentAxis
= espr_ShortTermConvertibleNotesIssuedNovember2012Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
   
Series A preferred stock warrant                  
Warrants                  
Warrants exercisable into stock (in shares)               1,940,000us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= espr_SeriesAPreferredStockWarrantMember
 
Exercise price (in dollars per share)               $ 1.00us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= espr_SeriesAPreferredStockWarrantMember
 
Number of shares of common stock to be purchased against outstanding warrants         277,690us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= espr_SeriesAPreferredStockWarrantMember
       
Series A preferred stock warrant | Total | Short term convertible notes issued September and November 2012                  
Warrants                  
Estimated fair value             300,000us-gaap_WarrantsAndRightsOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= espr_SeriesAPreferredStockWarrantMember
/ us-gaap_DebtInstrumentAxis
= espr_ShortTermConvertibleNotesIssuedSeptemberAndNovember2012Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
   
Common stock                  
Warrants                  
Exercise price (in dollars per share)                 $ 15.19us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
Common stock | Warrant                  
Warrants                  
Warrants exercisable into stock (in shares)               277,690us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
8,230us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
Fair value of warrants                 $ 100,000us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
Share price of common stock (in dollars per share)               $ 6.99us-gaap_SharePrice
/ us-gaap_ClassOfWarrantOrRightAxis
= us-gaap_WarrantMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember