Changes in Carrying Amount of Goodwill by Reportable Segment (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2017	Jan. 31, 2016	Apr. 30, 2017	Jul. 31, 2017	Jul. 31, 2016
Goodwill [Line Items]
Goodwill, Beginning Balance			$ 377,693	$ 377,693	$ 312,622
No activity				0
Goodwill acquired					74,184
Impairment charges	$ 0	$ (9,113)	0		(9,113)
Goodwill, Ending Balance				377,693	377,693
Towables
Goodwill [Line Items]
Goodwill, Beginning Balance			334,822	334,822	269,751
No activity				0
Goodwill acquired					74,184
Impairment charges					(9,113)
Goodwill, Ending Balance				334,822	334,822
Motorized
Goodwill [Line Items]
No activity				0
Other
Goodwill [Line Items]
Goodwill, Beginning Balance			$ 42,871	42,871	42,871
No activity				0
Goodwill, Ending Balance				$ 42,871	$ 42,871