Geographic Areas Information (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue		$ 111,600	$ 122,200	$ 131,500	$ 121,100	$ 138,100	$ 128,000	$ 127,900	$ 114,900	$ 486,372	$ 508,848	$ 540,291
Property, plant and equipment, net		102,676				107,790				102,676	107,790	106,300
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue										183,500	192,300	215,300
Property, plant and equipment, net		56,200				64,100				56,200	64,100	63,700
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue										67,400	66,700	51,100
Property, plant and equipment, net		20,400				20,400				20,400	20,400	19,600
GERMANY
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue										75,100	68,500	60,200
NETHERLANDS
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue										51,600	54,900	60,400
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue										108,800	126,400	153,300
Property, plant and equipment, net	[1]	7,600				6,900				7,600	6,900	7,400
DENMARK
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net		$ 18,500				$ 16,400				$ 18,500	$ 16,400	$ 15,600

[1] Other property, plant and equipment are primarily in Canada.