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Accounting Principles - Summary of Depreciation Periods (Detail)
12 Months Ended
Dec. 31, 2017
Fixtures and improvements in structures [member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Depreciation periods 9 years
Research and development / production tools [member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Depreciation periods 5 years
Research equipment and technical facilities [member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Depreciation periods 5 years
Computer equipment [member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Depreciation periods 3 years
Office equipment and furniture [member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Depreciation periods 5 years