Accumulated other comprehensive income (loss) (Details) $ in Thousands	3 Months Ended
	Apr. 01, 2017 USD ($)
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2016	$ 5,783,487
Balance as of April 1, 2017	6,064,824
Foreign currency translation adjustments
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2016	(825,354)
Current period other comprehensive income (loss) before reclassifications	83,623
Balance as of April 1, 2017	(741,731)
Pensions
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2016	(7,673)
Current period other comprehensive income (loss) before reclassifications	(582)
Balance as of April 1, 2017	(8,255)
AOCI attributable to parent
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2016	(833,027)
Current period other comprehensive income (loss) before reclassifications	83,041
Balance as of April 1, 2017	$ (749,986)