Product Warranty Liability (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Apr. 30, 2014	Jul. 31, 2013
Product Liability Contingency [Line Items]
Product warranty liability, beginning balance	$ 6.5	$ 5.6
Provision	3.1	5.3
Ultrasonix warranty accrual acquired		1.2
Settlements made in cash or in kind during the period	(3.4)	(5.6)
Product warranty liability, ending balance	$ 6.2	$ 6.5