Intangible Assets (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2011	Apr. 30, 2010	Jul. 31, 2010	Apr. 30, 2011 Technologies [Member]	Jul. 31, 2010 Technologies [Member]	Apr. 30, 2011 Customer relationships [Member]	Jul. 31, 2010 Customer relationships [Member]	Apr. 30, 2011 Trademarks and other [Member]	Jul. 31, 2010 Trademarks and other [Member]
Weighted Average Amortization Period						10.0	10.6	10.0	9.9	17.5	17.6
Gross Carrying Amount	$ 83,669,000		$ 83,669,000		$ 78,199,000	$ 47,694,000	$ 42,224,000	$ 29,931,000	$ 29,931,000	$ 6,044,000	$ 6,044,000
Accumulated Amortization	36,172,000		36,172,000		30,108,000	25,883,000	22,531,000	8,524,000	6,223,000	1,765,000	1,354,000
Net Carrying Amount	47,497,000		47,497,000		48,091,000	21,811,000	19,693,000	21,407,000	23,708,000	4,279,000	4,690,000
Total business acquisition purchase price	5,303,000		5,303,000
Fair value of contingent consideration arrangement	3,803,000		3,803,000
Term, in years, of contingent consideration arrangement			3
Business acquisition purchase price paid			1,500,000
Payment of contingent consideration related to business acquisition			8,000	0
Business acquisition, contingent consideration at fair value, noncurrent	3,574,000		3,574,000
Business acquisition, contingent consideration at fair value, current	492,000		492,000
Business acquisition, contingent consideration at fair value, accretion expense	118,000		271,000
Useful life, in years			5
Amortization Expense	2,173,000	1,754,000	6,064,000	5,283,000
Amortization Expense - Current Fiscal Year			8,091,000
Amortization Expense - Year Two			6,637,000
Amortization Expense - Year Three			6,327,000
Amortization Expense - Year Four			6,285,000
Amortization Expense - Year Five			$ 6,211,000