Reportable Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Product revenue:
Product Revenue										$ 502,752	$ 531,161	$ 509,527
Engineering revenue:
Engineering Revenue										6,096	9,130	8,021
Net revenue:
Total net revenue		$ 138,100	$ 128,000	$ 127,900	$ 114,900	$ 154,500	$ 133,600	$ 133,900	$ 118,300	508,848	540,291	517,548
Income from operations:
Income (loss) from operations										25,213	40,599	29,088
Total other income, net										(4,897)	434	(50)
Income before income taxes										20,316	41,033	29,038
Identifiable total assets by segment:
Assets		632,897				624,579				632,897	624,579
Goodwill by segment:
Goodwill		73,915				57,450				73,915	57,450
Share-based compensation expense:
Share based compensation										8,864	10,938	11,512
Depreciation and amortization:
Depreciation and amortization										23,500	23,300	22,100
Total Identifiable Assets
Identifiable total assets by segment:
Assets	[1]	559,000				570,500				559,000	570,500
Reportable segments
Identifiable total assets by segment:
Assets		393,400				414,100				393,400	414,100
Corporate
Identifiable total assets by segment:
Identifiable assets (excluding goodwill)	[2]	165,600				156,400				165,600	156,400
Medical Imaging
Product revenue:
Product Revenue										285,800	288,600	291,300
Engineering revenue:
Engineering Revenue										3,400	4,000	4,300
Net revenue:
Total net revenue										289,200	292,600	295,600
Income from operations:
Income (loss) from operations	[3]									38,600	37,900	31,000
Share-based compensation expense:
Share based compensation										3,900	4,900	6,600
Depreciation and amortization:
Depreciation and amortization										11,300	11,100	11,500
Medical Imaging | Reportable segments
Identifiable total assets by segment:
Assets	[4]	191,100				194,300				191,100	194,300
Goodwill by segment:
Goodwill		1,900				1,900				1,900	1,900
Ultrasound
Product revenue:
Product Revenue										160,800	163,600	152,300
Engineering revenue:
Engineering Revenue										2,400	2,600	200
Net revenue:
Total net revenue										163,200	166,200	152,500
Income from operations:
Income (loss) from operations	[5]									(18,800)	(7,900)	(6,800)
Share-based compensation expense:
Share based compensation										2,600	3,200	2,800
Depreciation and amortization:
Depreciation and amortization										10,400	10,500	9,100
Ultrasound | Reportable segments
Identifiable total assets by segment:
Assets	[6]	152,500				169,400				152,500	169,400
Goodwill by segment:
Goodwill		71,500				55,100				71,500	55,100
Security and Detection
Product revenue:
Product Revenue										56,100	79,000	65,900
Engineering revenue:
Engineering Revenue										300	2,500	3,500
Net revenue:
Total net revenue										56,400	81,500	69,400
Income from operations:
Income (loss) from operations	[7]									5,400	10,600	4,900
Share-based compensation expense:
Share based compensation										2,300	2,800	2,100
Depreciation and amortization:
Depreciation and amortization										1,800	1,700	$ 1,500
Security and Detection | Reportable segments
Identifiable total assets by segment:
Assets	[8]	49,800				50,400				49,800	50,400
Goodwill by segment:
Goodwill		$ 500				$ 500				$ 500	$ 500

[1] The Company in the past included the balance of goodwill in identifiable assets by segment table, but felt it more relevant to disclose the identifiable assets by segment excluding the associated goodwill balances as the goodwill balances are separately stated by segment. As such, the prior period presentation was modified to exclude the associated goodwill balances as well for comparability purposes.

[2] Includes cash, cash equivalents and marketable securities of $97.3 million and $86.2 million, as of July 31, 2016 and 2015, respectively.

[3] Includes restructuring charges of $6.0 million, $(0.2) million and $1.7 million for fiscal years 2016, 2015 and 2014, respectively.

[4] Includes net intangible assets from acquisitions of $20.3 million and 23.2 million at July 31, 2016 and 2015, respectively.

[5] Includes restructuring charges of $1.9 million, $(0.1) million and $1.4 million for fiscal year 2016, 2015 and 2014, respectively. Includes a $10.1 million and $1.0 million charge for the BK Medical matter for fiscal year 2016 and 2015, respectively

[6] Includes net intangible assets from acquisitions of $15.2 million and $15.2 million at July 31, 2016 and 2015, respectively, of which $3.7 million net intangible assets relating to our acquisition of Oncura during the second quarter of fiscal year 2016.

[7] Includes restructuring charges of $1.7 million, $(0.1) million and $0.4 million for fiscal year 2016, 2015 and 2014, respectively.

[8] Includes net intangible assets from acquisitions of $0.6 million and $0.1 million at July 31, 2016 and 2015, respectively, relating to our acquisition of Pathfinder during the first quarter of fiscal year 2015.