Annual report pursuant to Section 13 and 15(d)

Debt (Details 2)

v2.4.1.9
Debt (Details 2) (Unsecured debt, Credit Agreement, USD $)
In Thousands, unless otherwise specified
0 Months Ended 12 Months Ended
Dec. 08, 2014
Jun. 19, 2014
Dec. 31, 2014
Dec. 08, 2014
Dec. 07, 2014
Jun. 19, 2014
Revolving credit facility
           
Debt            
Credit facility amount $ 100,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
$ 70,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
  $ 100,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
$ 70,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
$ 70,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
Increase credit facility, amount 25,000env_LineOfCreditFacilityMaximumBorrowingCapacityContingentRightToIncreaseMaximumBorrowingCapacityAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
25,000env_LineOfCreditFacilityMaximumBorrowingCapacityContingentRightToIncreaseMaximumBorrowingCapacityAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
  25,000env_LineOfCreditFacilityMaximumBorrowingCapacityContingentRightToIncreaseMaximumBorrowingCapacityAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
  25,000env_LineOfCreditFacilityMaximumBorrowingCapacityContingentRightToIncreaseMaximumBorrowingCapacityAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
Commitment fee 0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
       
Amount outstanding     0us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
     
Interest expense     259us-gaap_InterestExpenseDebt
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
     
Revolving credit facility | LIBOR | Minimum
           
Debt            
Spread on variable rate basis 1.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
1.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
       
Revolving credit facility | LIBOR | Maximum
           
Debt            
Spread on variable rate basis 3.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
       
Letter of credit
           
Debt            
Credit facility amount $ 5,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
$ 5,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
  $ 5,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
  $ 5,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ us-gaap_DebtInstrumentAxis
= env_CreditAgreementMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember