Reportable Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Product revenue:
Product Revenue										$ 531,161	$ 509,527	$ 526,725
Engineering revenue:
Engineering Revenue										9,130	8,021	23,638
Net revenue:
Total net revenue		$ 154,500	$ 133,600	$ 133,900	$ 118,300	$ 142,000	$ 124,000	$ 141,400	$ 110,100	540,291	517,548	550,363
Income from operations:
Income (loss) from operations										40,599	29,088	45,375
Total other income, net										434	(50)	(1,278)
Income before income taxes										41,033	29,038	44,097
Identifiable assets by segment:
Assets		627,970				614,342				627,970	614,342
Goodwill by segment:
Goodwill		57,450				56,955				57,450	56,955
Share-based compensation expense:
Share based compensation										10,938	11,512	11,601
Depreciation and amortization:
Depreciation and amortization										23,307	22,057	17,275
Reportable segments
Identifiable assets by segment:
Assets		471,600				489,000				471,600	489,000
Corporate
Identifiable assets by segment:
Assets	[1]	156,400				125,300				156,400	125,300
Medical Imaging
Product revenue:
Product Revenue										288,600	291,300	305,600
Engineering revenue:
Engineering Revenue										4,000	4,300	13,000
Net revenue:
Total net revenue										292,600	295,600	318,600
Income from operations:
Income (loss) from operations	[2]									37,900	31,000	31,900
Share-based compensation expense:
Share based compensation										4,900	6,600	7,600
Depreciation and amortization:
Depreciation and amortization										11,100	11,500	11,500
Medical Imaging | Reportable segments
Identifiable assets by segment:
Assets	[3]	196,200				218,500				196,200	218,500
Goodwill by segment:
Goodwill		1,900				1,900				1,900	1,900
Ultrasound
Product revenue:
Product Revenue										163,600	152,300	149,600
Engineering revenue:
Engineering Revenue										2,600	200	200
Net revenue:
Total net revenue										166,200	152,500	149,800
Income from operations:
Income (loss) from operations	[4]									(7,900)	(6,800)	(3,700)
Share-based compensation expense:
Share based compensation										3,200	2,800	2,100
Depreciation and amortization:
Depreciation and amortization										10,500	9,100	4,700
Ultrasound | Reportable segments
Identifiable assets by segment:
Assets	[5]	224,500				235,500				224,500	235,500
Goodwill by segment:
Goodwill		55,100				55,100				55,100	55,100
Security Technology
Share-based compensation expense:
Share based compensation										2,800	2,100	1,900
Depreciation and amortization:
Depreciation and amortization										1,700	1,500	1,100
Security and Detection
Product revenue:
Product Revenue										79,000	65,900	71,600
Engineering revenue:
Engineering Revenue										2,500	3,500	10,400
Net revenue:
Total net revenue										81,500	69,400	82,000
Income from operations:
Income (loss) from operations	[6]									10,600	4,900	$ 17,200
Security and Detection | Reportable segments
Identifiable assets by segment:
Assets	[7]	50,900				$ 35,000				50,900	$ 35,000
Goodwill by segment:
Goodwill		$ 500								$ 500

[1] Includes cash, cash equivalents and marketable securities of $86.2 million and $60.9 million, as of July 31, 2015 and 2014, respectively.

[2] Includes restructuring charges of $(0.2) million, $1.7 million and $1.1 million for fiscal years 2015, 2014 and 2013, respectively.

[3] Includes net intangible assets from acquisitions of $23.2 million and $26.0 million at July 31, 2015 and 2014, respectively.

[4] Includes restructuring charges of $(0.1) million, $1.4 million and $2.2 million for fiscal year 2015, 2014 and 2013, respectively. Includes a $1.0 million charge for a settlement proposal with the SEC, related to our Danish Subsidiary BK Medical

[5] Includes net intangible assets from acquisitions of $15.2 million and $19.9 million at July 31, 2015 and 2014, respectively.

[6] Includes restructuring charges of $(0.1) million, $0.4 million and $0.2 million for fiscal year 2015, 2014 and 2013, respectively.

[7] Includes net intangible assets from acquisitions of $0.1 million at July 31, 2015, relating to our acquisition of Pathfinder during the first quarter of fiscal year 2015.