Acquisitions - Additional Information (Detail) (USD $)	9 Months Ended		1 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Jul. 31, 2013	Aug. 31, 2014
Business Acquisition [Line Items]
Business acquisition total consideration, net of cash acquired	$ 2,949,000	$ 10,175,000
Global Ascent, Inc.
Business Acquisition [Line Items]
Business acquisition, contingent consideration			1,900,000
Business acquisition, purchase price			12,900,000
Business acquisition, net working capital			1,300,000
Business acquisition, allocated to goodwill and intangible assets			11,600,000
Business acquisition, expected deductible goodwill recognized for tax purposes			9,200,000
Business acquisition, Contingent consideration based upon achievement of operating earnings thresholds			4,000,000
Business acquisition, contingent consideration thresholds period			6 years
Mechanical Service | UNITED KINGDOM
Business Acquisition [Line Items]
Business acquisition total consideration, net of cash acquired				2,900,000
Business acquisitions, cash acquired				200,000
Business acquisition, contingent consideration				100,000
Business acquisition, allocated to fixed assets and net working capital				2,400,000
Business acquisition, intangible assets				$ 800,000