Reportable Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015	Jul. 31, 2015
Product revenue:
Product Revenue		$ 125,938	$ 131,272	$ 240,067	$ 248,207
Engineering revenue:
Engineering Revenue		1,931	2,673	2,750	4,054
Net Revenue:
Total net revenue		127,869	133,945	242,817	252,261
Income from operations:
Income from operations		1,509	12,301	3,497	17,258
Total other income (expense), net		(3,500)	(200)	(4,000)	(100)
(Loss) Income before income taxes		(1,998)	12,132	(468)	17,207
Identifiable assets by segment:
Assets		635,158		635,158		$ 624,579
Goodwill by segment:
Goodwill		73,791		73,791		57,450
Assets, Total
Identifiable assets by segment:
Assets		561,400		561,400		570,500
Reportable segments
Identifiable assets by segment:
Assets		395,000		395,000		414,100
Corporate
Identifiable assets by segment:
Identifiable assets (excluding goodwill)	[1]	166,400		166,400		156,400
Medical Imaging
Product revenue:
Product Revenue		72,400	71,800	136,800	138,100
Engineering revenue:
Engineering Revenue		1,100	1,300	1,700	1,800
Net Revenue:
Total net revenue		73,500	73,100	138,500	139,900
Income from operations:
Income from operations		11,600	9,400	18,000	16,800
Medical Imaging | Reportable segments
Identifiable assets by segment:
Assets		175,800		175,800		194,300
Goodwill by segment:
Goodwill		1,900		1,900		1,900
Ultrasound
Product revenue:
Product Revenue		42,600	41,800	79,100	79,100
Engineering revenue:
Engineering Revenue		700	700	900	1,200
Net Revenue:
Total net revenue		43,300	42,500	80,000	80,300
Income from operations:
Income from operations		(9,900)	200	(14,500)	(2,800)
Ultrasound | Reportable segments
Identifiable assets by segment:
Assets		171,700		171,700		169,400
Goodwill by segment:
Goodwill		71,400		71,400		55,100
Security and Detection
Product revenue:
Product Revenue		10,900	17,700	24,200	31,000
Engineering revenue:
Engineering Revenue		200	600	200	1,100
Net Revenue:
Total net revenue		11,100	18,300	24,400	32,100
Income from operations:
Income from operations		(200)	$ 2,700		$ 3,300
Security and Detection | Reportable segments
Identifiable assets by segment:
Assets		47,500		47,500		50,400
Goodwill by segment:
Goodwill		$ 500		$ 500		$ 500

[1] Includes cash and cash equivalents of $89.1 million and $86.2 million as of January 31, 2016 and July 31, 2015, respectively.