Restructuring and Related Charges by Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 0.2	$ 0.3	$ 0.7	$ 0.3
Medical Imaging
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges		0.1	0.1	0.1
Ultrasound
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 0.2	$ 0.2	$ 0.6	$ 0.2