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Acquisition - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended 0 Months Ended
Sep. 30, 2014
Oct. 31, 2014
Jan. 31, 2014
Business Acquisition [Line Items]      
Business acquired assets and liabilities     $ 5,220us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
Consideration paid 5,186esi_BusinessCombinationConsiderationPaid    
Subsequent Event [Member]      
Business Acquisition [Line Items]      
Consideration paid   $ 34esi_BusinessCombinationConsiderationPaid
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		  
Ascolta [Member]      
Business Acquisition [Line Items]      
Identifiable intangible assets weighted-average life 5 years