Changes in Carrying Amount of Goodwill by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 30, 2016	Jan. 31, 2016	Jul. 31, 2016	Jul. 31, 2015
Goodwill [Line Items]
Goodwill acquired			$ 74,184	$ 56,043
Impairment charges	$ 0	$ (9,113)	(9,113)
Goodwill, Ending Balance			377,693	312,622
Towables
Goodwill [Line Items]
Goodwill acquired			74,184	13,172
Impairment charges			(9,113)
Goodwill, Ending Balance			334,822	269,751
Other
Goodwill [Line Items]
Goodwill acquired				42,871
Goodwill, Ending Balance			$ 42,871	$ 42,871