Acquisitions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended		0 Months Ended				0 Months Ended
	Mar. 01, 2014 Alpha Mechanical, Inc. Purchase Price Allocation	Aug. 31, 2016 BEST Forecast	Sep. 01, 2013 BEST Purchase Price Allocation	Aug. 01, 2013 Blackjack Purchase Price Allocation	Nov. 01, 2012 Air Serv Purchase Price Allocation	Jul. 31, 2014 Air Serv Purchase Price Allocation	Nov. 01, 2012 HHA Purchase Price Allocation	Nov. 01, 2012 Calvert-Jones Purchase Price Allocation
Business Acquisition
Business acquisition aggregate purchase price	$ 12.3		$ 4.9	$ 5.2	$ 162.9		$ 33.7	$ 6.1
Business acquisition, cost of acquired entity, contingent consideration	0		1.6	0	0		0	0
Deferred consideration estimate value, high		2.0
Business acquisition indemnification hold back amount						$ 11.8