Restructuring Charges - Additional Information (Detail) $ in Thousands	12 Months Ended
	Jul. 31, 2017 USD ($) Employee	Jul. 31, 2016 USD ($) Employee	Jul. 31, 2015 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 7,167	$ 9,641	$ (354)
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	1,400	6,000	(200)
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	5,500	1,900	(100)
Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	300	1,700	$ (100)
Fiscal Year 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 7,200
Expected reduction in number of employees | Employee	130
Involuntarily terminated employees | Employee	130
Fiscal Year 2017 Restructuring Plan | Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 1,400
Fiscal Year 2017 Restructuring Plan | Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	5,500
Fiscal Year 2017 Restructuring Plan | Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 300
Fiscal Year 2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		$ 9,600
Involuntarily terminated employees | Employee		117
Fiscal Year 2016 Restructuring Plan | Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		$ 6,000
Fiscal Year 2016 Restructuring Plan | Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		1,900
Fiscal Year 2016 Restructuring Plan | Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		$ 1,700