Reportable Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015	Jul. 31, 2015
Product revenue:
Product Revenue		$ 126,376	$ 130,479	$ 366,443	$ 378,686
Engineering revenue:
Engineering Revenue		1,604	3,080	4,354	7,134
Net Revenue:
Total net revenue		127,980	133,559	370,797	385,820
Income from operations:
Income from operations		7,626	7,637	11,123	24,895
Total other (expense) income, net		(900)	200	(4,900)	100
Income before income taxes		6,692	7,838	6,224	25,045
Identifiable assets by segment:
Assets		645,927		645,927		$ 624,579
Goodwill by segment:
Goodwill		73,776		73,776		57,450
Assets, Total
Identifiable assets by segment:
Assets		572,200		572,200		570,500
Reportable segments
Identifiable assets by segment:
Assets		402,000		402,000		414,100
Corporate
Identifiable assets by segment:
Identifiable assets (excluding goodwill)	[1]	170,200		170,200		156,400
Medical Imaging
Product revenue:
Product Revenue		71,900	70,800	208,700	209,000
Engineering revenue:
Engineering Revenue		900	1,100	2,600	2,800
Net Revenue:
Total net revenue		72,900	71,900	211,300	211,800
Income from operations:
Income from operations		10,200	8,500	28,200	25,400
Medical Imaging | Reportable segments
Identifiable assets by segment:
Assets		183,200		183,200		194,300
Goodwill by segment:
Goodwill		1,900		1,900		1,900
Ultrasound
Product revenue:
Product Revenue		36,800	37,800	115,900	116,800
Engineering revenue:
Engineering Revenue		800	800	1,700	2,000
Net Revenue:
Total net revenue		37,600	38,600	117,600	118,800
Income from operations:
Income from operations		(5,000)	(4,200)	(19,500)	(7,100)
Ultrasound | Reportable segments
Identifiable assets by segment:
Assets		171,100		171,100		169,400
Goodwill by segment:
Goodwill		71,400		71,400		55,100
Security and Detection
Product revenue:
Product Revenue		17,600	21,900	41,800	52,900
Engineering revenue:
Engineering Revenue		(100)	1,200	100	2,300
Net Revenue:
Total net revenue		17,500	23,100	41,900	55,200
Income from operations:
Income from operations		2,400	$ 3,300	2,400	$ 6,600
Security and Detection | Reportable segments
Identifiable assets by segment:
Assets		47,700		47,700		50,400
Goodwill by segment:
Goodwill		$ 500		$ 500		$ 500

[1] Includes cash and cash equivalents of $92.0 million and $86.2 million as of April 30, 2016 and July 31, 2015, respectively.