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Segment Reporting and Related Disclosures - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended
Feb. 28, 2015
Customer
Segment
May 31, 2014
Revenue from External Customer [Line Items]    
Number of operating segment 2us-gaap_NumberOfOperatingSegments  
Number of major customer accounted for more than 10% of total revenues 0elrc_NumberOfCustomerForReportableSegment  
T&M    
Revenue from External Customer [Line Items]    
Equipment pool, based on acquisition cost 420,771elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_TestAndMeasurementEquipmentMember		 $ 421,128elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_TestAndMeasurementEquipmentMember
DP    
Revenue from External Customer [Line Items]    
Equipment pool, based on acquisition cost 37,501elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_DataProductsEquipmentMember		 $ 37,911elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_DataProductsEquipmentMember