Restructuring and Related Charges by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 270	$ 3,100	$ 300	$ 6,500
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	90	1,900	110	4,000
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	170	600	180	1,300
Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 10	$ 600	$ 10	$ 1,200