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Basis of Preparation - Schedule of Estimated Useful Lives And Depreciation Rates (Detail)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Bottom of range [member] | Engineering equipment [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 5 years 20 percent
Bottom of range [member] | Office equipment [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 5 years 20 percent
Bottom of range [member] | Other [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 5 years 10 percent
Top of range [member] | Engineering equipment [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 10 years 30 percent
Top of range [member] | Office equipment [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 10 years 30 percent
Top of range [member] | Other [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated lives/ Declining balance 50 years 30 percent