Income taxes - examination by major tax jurisdictions (Detail) - Ending	12 Months Ended
	Dec. 31, 2015
United States
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Canada
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
China
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Czech Republic
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
France
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Germany
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
India
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Ireland
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Italy
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Malaysia
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015
Singapore
Income Tax Examination [Line Items]
Taxable years remain subject to examination	2015