Stock-Based Compensation (Details) (USD $)	3 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Jul. 31, 2012
Stock-based compensation expense before income tax benefit	$ 745,000	$ 873,000
Income tax benefit	(264,000)	(306,000)
Net stock-based compensation expense	481,000	567,000
Stock-based compensation capitalized and included in ending inventory	48,000		48,000
Share-based Compensation Arrangement by Share-based Payment Award, Options or Units, Grants in Period, Gross	222
Targeted annual dividend per share	$ 1.10
Actual income tax benefit recorded for the tax deductions relating to the exercise of stock-based awards	1,000	120,000
Less: Tax benefit initially recognized on exercised stock-based awards vesting subsequent to the adoption of accounting standards that require us to expense stock-based awards, excluding income tax shortfalls	(1,000)	(99,000)
Excess income tax benefit recorded as an increase to additional paid-in capital	0	21,000
Less: Tax benefit initially disclosed but not previously recognized on exercised equity-classified stock-based awards vesting prior to the adoption of accounting standards that require us to expense stock-based awards	0	(2,000)
Excess income tax benefit from exercised equity-classified stock-based awards reported as a cash flow from financing activities in our Condensed Consolidated Statements of Cash Flows	0	19,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	8,514,000
Estimated forfeitures related to unvested stock-based awards	596,000
Weighted average number of years net compensation cost is expected to be recognized over	3 years 6 months 0 days
Hypothetical tax benefits related to stock-based awards	19,890,000
Reduction to APIC and accumulated hypothetical tax benefits, due to reversal of unrealized deferred tax assets associated with certain vested equity-classified stock-based awards expiring during the period	2,892,000	1,021,000
Stock Options [Member]
Stock-based compensation expense before income tax benefit	573,000	792,000
Per share weighted average grant date fair value of stock based awards granted		$ 5.88
Expected dividend yield		4.04%
Expected volatility		36.00%
Risk-free interest rate		0.88%
Expected life (in years)		5 years 5 months 1 day
Vesting period of stock-based awards granted		5 years
Contractual term (in years)		10 years
Targeted annual dividend per share		$ 1.10
Employee Stock Purchase Plan - ESPP [Member]
Stock-based compensation expense before income tax benefit	53,000	61,000
Discount offered to employees participating in the Employee stock purchase plan (ESPP) as a percentage of market price	15.00%	15.00%
Restricted Stock Units (RSUs) With Performance Measures [Member]
Stock-based compensation expense before income tax benefit	86,000	0
Vesting period of stock-based awards granted	5 years 3 months 19 days
Restricted Stock Units (RSUs) Without Performance Measures [Member]
Stock-based compensation expense before income tax benefit	32,000	0
Vesting period of stock-based awards granted	3 years
Stock Units [Member]
Stock-based compensation expense before income tax benefit	6,000	0
Weighted average grant date closing price of fully-vested stock units granted in period	$ 28.12
Liability-Classified Stock Appreciation Rights (SARs) [Member]
Stock-based compensation expense before income tax benefit	(5,000)	20,000
Vesting period of stock-based awards granted	3 years
Contractual term (in years)	5 years
Accrued expense related to the cash settlement of liability-classified stock appreciation rights	1,000		6,000
Cost of Sales [Member]
Stock-based compensation expense before income tax benefit	45,000	53,000
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense before income tax benefit	601,000	645,000
Research and Development Expense [Member]
Stock-based compensation expense before income tax benefit	$ 99,000	$ 175,000