Summary of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2012	May 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 35,891	$ 24,166
Accumulated Amortization	(7,445)	(5,658)
Net Carrying Amount	28,446	18,508
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	23,684	12,198
Accumulated Amortization	(3,179)	(1,973)
Net Carrying Amount	20,505	10,225
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,469	3,136
Accumulated Amortization	(3,084)	(2,844)
Net Carrying Amount	385	292
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,962	2,962
Accumulated Amortization	(282)	(207)
Net Carrying Amount	2,680	2,755
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,112	5,112
Accumulated Amortization	(900)	(634)
Net Carrying Amount	4,212	4,478
Licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	664	758
Net Carrying Amount	$ 664	$ 758