Segment Reporting and Related Disclosures - Additional Information (Detail) $ in Thousands	3 Months Ended
Aug. 31, 2015 USD ($) Segment Customer	May. 31, 2015 USD ($)
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
DP
Revenue from External Customer [Line Items]
Equipment pool, based on acquisition cost	$ 38,732	$ 37,824
T&M
Revenue from External Customer [Line Items]
Equipment pool, based on acquisition cost	$ 425,684	$ 434,963

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration