Intangible Assets (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015	Jul. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 82,995,000		$ 82,995,000		$ 82,995,000
Accumulated amortization	65,558,000		65,558,000		62,986,000
Net carrying amount	17,437,000		17,437,000		$ 20,009,000
Amortization of intangibles	1,196,000	$ 1,560,000	2,572,000	$ 3,121,000
Amortization expense - year one	4,962,000		4,962,000
Amortization expense - year two	4,782,000		4,782,000
Amortization expense - year three	4,782,000		4,782,000
Amortization expense - year four	862,000		862,000
Amortization expense - year five	862,000		$ 862,000
Technologies
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			13 years		12 years 1 month 6 days
Gross carrying amount	47,370,000		$ 47,370,000		$ 47,370,000
Accumulated amortization	40,245,000		40,245,000		39,266,000
Net carrying amount	7,125,000		$ 7,125,000		$ 8,104,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			10 years		10 years
Gross carrying amount	29,831,000		$ 29,831,000		$ 29,831,000
Accumulated amortization	22,456,000		22,456,000		20,981,000
Net carrying amount	7,375,000		$ 7,375,000		$ 8,850,000
Trademarks and other
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			20 years		20 years
Gross carrying amount	5,794,000		$ 5,794,000		$ 5,794,000
Accumulated amortization	2,857,000		2,857,000		2,739,000
Net carrying amount	$ 2,937,000		$ 2,937,000		$ 3,055,000