Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010
Income Taxes [Line Items]
Current federal tax expense, ending balance	$ 57,736	$ 48,943	$ 55,462
Current federal tax expense benefit period increase (decrease)	8,793	(6,519)
Increase in income taxes due to increase in pre-tax income	9,822
Increase (decrease) in pretax income	28,064	(18,766)
Increase (decrease) in current federal tax expense due reduced income tax credits and incentives	1,441
Increase (decrease) in current federal tax expense due to domestic manufacturing deduction	(409)	(1,491)
Increases (decrease) in various temporary items	(1,586)	1,207
Decrease in income taxes due to reduction in pre-tax income		(6,568)
Decrease in current federal tax expense due to disallowed executive compensation		(1,578)
Current state and local tax expense benefit period increase (decrease)	4,408	(9,087)
Current state tax expense	4,658	250	9,337
Current state and local tax expenses increase (decrease) due to increase (decrease) in pre-tax income	617	(657)
Increase (decrease) in current state tax expense due to increase (decrease) in unrecognized tax benefits	4,244	(2,329)
Current state tax expense increase decrease in various temporary items		232
Decrease in current state tax expenses result of reduction in company's state blended tax rate and increased income tax credits		(3,731)
Current state tax expense decrease due to disallowed executive compensation		(212)
Income before income taxes includes foreign income (loss)			(8,154)
Increase (decrease) in net deferred tax assets	3,234
Net deferred tax assets, ending balance	19,963	16,729
Increase (decrease) in deferred tax assets due to increased (decreased) intangibles liability	(1,989)
Increase in deferred tax asset due to increase in product warranty reserves	2,247
Changes in deferred tax assets offset by increase (decrease) in accrued expenses	(1,539)
Capital loss carry forward expected to be realized prior to expiration	143
Unrecognized tax benefits that, if recognized, would affect the company's income tax rate	22,454	21,453	20,719
Total amount of liabilities accrued for interest and penalties related to unrecognized tax benefits	13,265	12,533	13,326
Total amount of interest and penalties expense (benefit) recognized	503	(995)	(2,200)
Expected decrease in unrecognized tax benefits due to resolution of uncertain tax positions	3,700
Expected decrease in interest due to resolution of uncertain tax positions	900
Expected decrease in penalties due to resolution of uncertain tax positions	40
Minimum
Income Taxes [Line Items]
Gross decrease in unrecognized tax benefit	3,200
Decrease in accrued interest and penalties	1,800
Maximum
Income Taxes [Line Items]
Gross decrease in unrecognized tax benefit	13,100
Decrease in accrued interest and penalties	5,800
Oregon State
Income Taxes [Line Items]
Tax and interest paid to finalize tax audit for tax years ended July 31, 2006 through 2008	113
Michigan
Income Taxes [Line Items]
Tax and interest paid to finalize tax audit for tax years ended July 31, 2006 through 2008	$ 7