Restructuring and Related Charges by Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 3.1	$ (0.1)	$ 6.5	$ (0.2)
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	1.9	$ (0.1)	4.0	(0.1)
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	0.6		1.3	$ (0.1)
Security and Detection
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 0.6		$ 1.2