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Segment Reporting and Related Disclosures - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Nov. 30, 2014
Customer
Segment
Nov. 30, 2013
Customer
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 0elrc_NumberOfCustomerForReportableSegment  
T&M      
Revenue from External Customer [Line Items]      
Equipment pool, based on acquisition cost 421,539elrc_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 38,118elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_DataProductsEquipmentMember		   $ 37,911elrc_RentalAndLeaseEquipment
/ us-gaap_ProductOrServiceAxis
= elrc_DataProductsEquipmentMember