Segment Reporting and Related Disclosures - Additional Information (Detail) $ in Thousands	12 Months Ended
	May. 31, 2015 USD ($) Segment Customer	May. 31, 2014 USD ($) Customer	May. 31, 2013 Customer
Revenue from External Customer [Line Items]
Number of operating segment | Segment	2
Number of major customer accounted for more than 10% of total revenues | Customer	0	0	0
T&M equipment
Revenue from External Customer [Line Items]
Equipment pool, based on acquisition cost	$ 434,963	$ 421,128
DP equipment
Revenue from External Customer [Line Items]
Equipment pool, based on acquisition cost	$ 37,824	$ 37,911