Summary of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 36,798	$ 36,211
Accumulated Amortization	(13,585)	(12,698)
Net Carrying Amount	23,213	23,513
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	23,029	22,424
Accumulated Amortization	(7,373)	(6,739)
Net Carrying Amount	15,656	15,685
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,649	3,667
Accumulated Amortization	(3,459)	(3,430)
Net Carrying Amount	190	237
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,325	4,325
Accumulated Amortization	(792)	(717)
Net Carrying Amount	3,533	3,608
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,112	5,112
Accumulated Amortization	(1,831)	(1,698)
Net Carrying Amount	3,281	3,414
Licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	683	683
Accumulated Amortization	(130)	(114)
Net Carrying Amount	$ 553	$ 569