Summary of Significant Accounting Policies - additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012 Day Segment	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Significant Accounting Policies [Line Items]
Number of reportable segments	3
Cash and cash equivalents	$ 218,642	$ 215,435	$ 247,751	$ 221,684
Depreciation expense	13,843	13,747	12,719
Self-insured retention for products liability and personal injury matters	5,000
Self insurance retention for bus related matters	7,500
Excess liability insurance	50,000
Payments received on sale of products within days	15
Advertising costs	7,863	7,149	5,377
Maximum percentage of tax benefits realized upon ultimate settlement	50.00%
Antidilutive stock options outstanding	412,000	729,826	784,000
Dealer Networks
Significant Accounting Policies [Line Items]
Intangible assets amortization period, minimum years	12
Intangible assets amortization period, maximum years	14
Design Technology Assets
Significant Accounting Policies [Line Items]
Intangible assets amortization period, minimum years	5
Intangible assets amortization period, maximum years	15
Non-Compete Agreements
Significant Accounting Policies [Line Items]
Intangible assets amortization period, minimum years	5
Intangible assets amortization period, maximum years	15
Trademarks
Significant Accounting Policies [Line Items]
Intangible assets amortization period, minimum years	20
Intangible assets amortization period, maximum years	25
Buildings And Improvements
Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life, minimum years	10
Property, plant and equipment, estimated useful life, maximum years	39
Machinery and Equipment
Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life, minimum years	3
Property, plant and equipment, estimated useful life, maximum years	10
Selling, General And Administrative Expenses
Significant Accounting Policies [Line Items]
Depreciation expense	3,175	3,022	2,545
Maximum
Significant Accounting Policies [Line Items]
Cash equivalents maturity period	3 months
Option vesting period	5 years
Minimum
Significant Accounting Policies [Line Items]
Option vesting period	3 years
Held By One Financial Institution
Significant Accounting Policies [Line Items]
Cash and cash equivalents	183,615	181,012
Held At Various Other Financial Institutions
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 35,027	$ 34,423