Commitments, guarantees and contingencies - Additional Information (Detail) CAD in Thousands				1 Months Ended		12 Months Ended
	Jan. 03, 2017 CAD	Nov. 23, 2015 USD ($)	Oct. 11, 2011 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2017 CAD	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Liabilities related to agreements						$ 0
Deferred revenue						6,800,000	$ 7,200,000
Revolving credit agreement period		5 years
Interest expense							3,200,000	$ 600,000
Ultrasonix
Commitments and Contingencies Disclosure [Line Items]
Settlement amount agreed to pay				$ 600,000	CAD 775
Ultrasonix | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Unpaid and accelerated rent legal claim | CAD	CAD 1,000
Ultrasonix | General and Administrative
Commitments and Contingencies Disclosure [Line Items]
Settlement amount agreed to pay						600,000
Twenty-four Former Interest-holders of Oncura Partners Diagnostics, LLC | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Excess of unspecified damages						1,000,000
Other Liabilities
Commitments and Contingencies Disclosure [Line Items]
Asset retirement obligations, estimated cost of restoring our leased facilities						$ 1,300,000	1,100,000
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%
Interest expense						$ 0
Credit facility transaction costs incurred						$ 500,000
Credit facility, maturity period						5 years
Line of credit amount outstanding						$ 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
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						$ 400,000	$ 200,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term						12 months
Minimum | Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Credit facility commitment fee percentage		0.20%
Interest coverage ratio						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 | 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%