Reportable Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Jul. 31, 2017
Product revenue:
Product revenue	$ 105,752	$ 120,245
Engineering revenue:
Engineering revenue	1,123	873
Net revenue:
Total net revenue	106,875	121,118
Income (loss) from operations:
Total (loss) income from operations	7,874	3,953
Total other income (loss), net	200	(400)
Income before income taxes	8,112	3,511
Identifiable total assets by segment:
Assets	537,331		$ 538,083
Total Identifiable Assets
Identifiable total assets by segment:
Assets	535,000		535,700
Reportable segments
Identifiable total assets by segment:
Assets	332,000		338,700
Corporate
Identifiable total assets by segment:
Identifiable assets (excluding goodwill)	203,000		197,000
Medical Imaging
Product revenue:
Product revenue	52,000	66,500
Engineering revenue:
Engineering revenue	1,100	700
Net revenue:
Total net revenue	53,100	67,200
Income (loss) from operations:
Total (loss) income from operations	4,800	6,700
Medical Imaging | Reportable segments
Identifiable total assets by segment:
Assets	159,600		169,100
Ultrasound
Product revenue:
Product revenue	37,400	35,600
Engineering revenue:
Engineering revenue		200
Net revenue:
Total net revenue	37,400	35,800
Income (loss) from operations:
Total (loss) income from operations	1,300	(5,800)
Ultrasound | Reportable segments
Identifiable total assets by segment:
Assets	132,700		133,600
Security and Detection
Product revenue:
Product revenue	16,400	18,100
Net revenue:
Total net revenue	16,400	18,100
Income (loss) from operations:
Total (loss) income from operations	1,800	$ 3,000
Security and Detection | Reportable segments
Identifiable total assets by segment:
Assets	$ 39,700		$ 36,000