Restructuring and Related Charges by Segment (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 2.1	$ 0.7	$ 2.4
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	0.2	0.1	0.4
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	1.8	$ 0.6	1.9
Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 0.1		$ 0.1