Restructuring and Related Charges by Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 7.2	$ 9.6	$ (0.4)
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	1.4	6.0	(0.2)
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	5.5	1.9	(0.1)
Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 0.3	$ 1.7	$ (0.1)