Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details 3)

v2.4.1.9
Fair Value Measurements (Details 3) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Unsecured debt | 1.75% convertible unsecured notes due December 2019  
Carrying amounts and estimated fair values of financial instruments not recorded at fair value  
Face amount $ 172,500env_DebtInstrumentFaceAmountAndOverAllotments
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Carrying Value  
Carrying amounts and estimated fair values of financial instruments not recorded at fair value  
2019 Convertible Notes 145,203us-gaap_DebtInstrumentFairValue
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Fair Value | Level 1  
Carrying amounts and estimated fair values of financial instruments not recorded at fair value  
2019 Convertible Notes $ 180,392us-gaap_DebtInstrumentFairValue
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