Reportable Segment Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Apr. 30, 2015		Apr. 30, 2014	Apr. 30, 2015		Apr. 30, 2014	Jul. 31, 2014
Product revenue:
Product Revenue	$ 130,479		$ 122,067	$ 378,686		$ 369,992
Engineering revenue:
Engineering Revenue	3,080		1,965	7,134		5,559
Net Revenue:
Total net revenue	133,559		124,032	385,820		375,551
Income from operations:
Income (loss) from operations	7,637		9,417	24,895		17,136
Total other income, net	201		882	150		104
Income before income taxes	7,838		10,299	25,045		17,240
Identifiable assets by segment:
Assets	624,536			624,536			614,342
Goodwill by segment:
Goodwill	57,358			57,358			56,955
Reportable segments
Identifiable assets by segment:
Assets	470,600			470,600			489,000
Corporate
Identifiable assets by segment:
Assets	153,900	[1]		153,900	[1]		125,300	[1]
Medical Imaging
Product revenue:
Product Revenue	70,800		70,700	209,000		208,300
Engineering revenue:
Engineering Revenue	1,100		1,000	2,800		3,200
Net Revenue:
Total net revenue	71,900		71,700	211,800		211,500
Income from operations:
Income (loss) from operations	8,500		8,900	25,400		19,300
Medical Imaging | Reportable segments
Identifiable assets by segment:
Assets	191,600			191,600			218,500
Goodwill by segment:
Goodwill	1,900			1,900			1,900
Ultrasound
Product revenue:
Product Revenue	37,800		37,300	116,800		112,100
Engineering revenue:
Engineering Revenue	800			2,000
Net Revenue:
Total net revenue	38,600		37,300	118,800		112,100
Income from operations:
Income (loss) from operations	(4,200)		(1,300)	(7,100)		(6,100)
Ultrasound | Reportable segments
Identifiable assets by segment:
Assets	230,000			230,000			235,500
Goodwill by segment:
Goodwill	55,100			55,100			55,100
Security and Detection
Product revenue:
Product Revenue	21,900		14,100	52,900		49,600
Engineering revenue:
Engineering Revenue	1,200		1,000	2,300		2,400
Net Revenue:
Total net revenue	23,100		15,100	55,200		52,000
Income from operations:
Income (loss) from operations	3,300		1,800	6,600		3,900
Security and Detection | Reportable segments
Identifiable assets by segment:
Assets	49,000			49,000			35,000
Goodwill by segment:
Goodwill	$ 400	[2]		$ 400	[2]

[1] Includes cash and cash equivalents of $82.8 million and $60.9 million as of April 30, 2015 and July 31, 2014, respectively.

[2] Includes goodwill related to the Pathfinder acquisition as described in Note 3, Business Combinations.