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%