Guarantees, Commitments and Contingencies - Additional Information (Detail) CAD in Millions				3 Months Ended	9 Months Ended
	Jan. 03, 2017 CAD	Nov. 23, 2015 USD ($)	Oct. 11, 2011 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jul. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Liabilities related to agreements				$ 0	$ 0
Revolving credit agreement period		5 years
Ultrasonix | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Unpaid and accelerated rent legal claim | CAD	CAD 1.0
Accrued charge in connection				$ 400,000	$ 400,000
Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Credit facility maximum borrow capacity		$ 100,000,000
Credit facility, expiry date					Nov. 23, 2020
Leverage ratio				0.40%	0.40%
Interest expense					$ 0
Credit facility transaction costs incurred				$ 500,000	$ 500,000
Credit facility, maturity period					5 years
Line of credit amount outstanding				0	$ 0	$ 0
Revolving Credit Facility | Other Revolving Credit Facilities
Commitments and Contingencies Disclosure [Line Items]
Credit facility available borrowing capacity				1,200,000	$ 1,200,000	1,200,000
Revolving Credit Facility Termination | Facility Exit Costs
Commitments and Contingencies Disclosure [Line Items]
Revolving credit agreement period			5 years
Credit facility maximum borrow capacity			$ 100,000,000
Credit facility, expiry date					Oct. 11, 2011
Product Extended Warranty Contracts
Commitments and Contingencies Disclosure [Line Items]
Deferred revenue				300,000	$ 300,000	$ 200,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term					12 months
Minimum | Ultrasonix | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Reasonable estimate of liability				$ 400,000	$ 400,000
Minimum | Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Credit facility commitment fee percentage		0.20%
Interest coverage ratio				300.00%	300.00%
Minimum | Revolving Credit Facility | LIBOR Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.25%
Minimum | Revolving Credit Facility | Base Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		0.00%
Maximum
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term					60 months
Maximum | Ultrasonix | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Reasonable estimate of liability				$ 700,000	$ 700,000
Maximum | Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Aggregate available credit amount under specified circumstances		$ 200,000,000
Credit facility commitment fee percentage		0.35%
Leverage ratio of total debt to earnings before interest, taxes, depreciation, and amortization or EBITDA					275.00%
Maximum | Revolving Credit Facility | LIBOR Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.75%
Maximum | Revolving Credit Facility | Base Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.00%