Accumulated other comprehensive income (loss) (Details) $ in Thousands		6 Months Ended
		Jul. 04, 2015 USD ($)
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2014		$ (429,321)
Current period other comprehensive income (loss) before reclassifications		(196,251)
Balance as of July 4, 2015		(625,572)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2014		(428,505)
Current period other comprehensive income (loss) before reclassifications		(196,333)
Balance as of July 4, 2015		(624,838)
Pensions
Accumulated Other Comprehensive Income Rollforward [Roll Forward]
Balance as of December 31, 2014	[1]	(816)
Current period other comprehensive income (loss) before reclassifications	[1]	82
Balance as of July 4, 2015	[1]	$ (734)

[1] This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost (refer to Note 13 to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014).