Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details 3)

v2.4.1.9
Fair Value Measurements (Details 3) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Unsecured debt | Convertible Notes    
Carrying amounts and estimated fair values of financial instruments not recorded at fair value    
Face amount $ 172,500env_DebtInstrumentFaceAmountAndOverAllotments
/ us-gaap_DebtInstrumentAxis
= env_ConvertibleUnsecured1.75PercentNotesDueDecember2019Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember 		$ 172,500env_DebtInstrumentFaceAmountAndOverAllotments
/ us-gaap_DebtInstrumentAxis
= env_ConvertibleUnsecured1.75PercentNotesDueDecember2019Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
Carrying Value    
Carrying amounts and estimated fair values of financial instruments not recorded at fair value    
2019 Convertible Notes 146,411us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember 		 
Fair Value | Level 1    
Carrying amounts and estimated fair values of financial instruments not recorded at fair value    
2019 Convertible Notes $ 195,489us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember