Goodwill and Intangible Assets - Additional Information (Detail)		3 Months Ended		6 Months Ended
	Dec. 31, 2016 USD ($)	Jan. 31, 2017 USD ($)	Jan. 31, 2016 USD ($)	Jan. 31, 2017 USD ($) Segment Unit	Jan. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)
Goodwill and Intangible Assets Disclosure [Line Items]
Indefinite lived intangible assets		$ 7,600,000		$ 7,600,000		$ 7,600,000
Amortization expense related to acquired intangible assets		2,000,000	$ 2,000,000	4,000,000	$ 4,000,000
Carrying value of intangible assets		33,000,000		33,000,000		37,600,000
Goodwill		64,105,000		$ 64,105,000		73,915,000
Number of Reporting Units | Unit				4
Number of Reportable Segments | Segment				3
Impairment of goodwill				$ 9,800,000
Other intangible assets		40,644,000		40,644,000		45,194,000
Developed technologies
Goodwill and Intangible Assets Disclosure [Line Items]
Carrying value of intangible assets		12,700,000		12,700,000		14,800,000
Trade names
Goodwill and Intangible Assets Disclosure [Line Items]
Carrying value of intangible assets		700,000		700,000		900,000
Medical Imaging
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill		1,900,000		1,900,000		1,900,000
Impairment of goodwill	$ 0
Ultrasound
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill	55,100,000	61,700,000		61,700,000		71,500,000
Impairment of goodwill	$ 0			9,800,000
Percentage of goodwill excess fair value over carrying value	25.00%
Security and Detection
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible assets impairment charge				600,000
Carrying value of intangible assets		600,000		600,000
Goodwill		500,000		500,000		$ 500,000
Impairment of goodwill				0
Security and Detection | Developed technologies
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible assets impairment charge				500,000
Security and Detection | Trade names
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible assets impairment charge				100,000
Oncura
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill		6,600,000		6,600,000
Impairment of goodwill		9,800,000
Other intangible assets		$ 3,300,000		3,300,000
Oncura | General and Administrative
Goodwill and Intangible Assets Disclosure [Line Items]
Gain from contingent consideration				$ 8,100,000
Minimum
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible assets, estimated useful lives		1 year
Maximum
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible assets, estimated useful lives		14 years