Changes in shareholders' equity Change in accumulated other comprehensive income , net of tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2016	Mar. 29, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,011,093
Amounts reclassified from accumulated other comprehensive (loss) income	2,586	$ 897
Ending Balance	2,061,198
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(2,491)	0
Other comprehensive income (loss) before reclassifications	(50)	243
Amounts reclassified from accumulated other comprehensive (loss) income	1,530	(199)
Net current-period other comprehensive income	1,480	44
Ending Balance	(1,011)	44
Pension and Other Postretirement Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(138,887)	(141,744)
Other comprehensive income (loss) before reclassifications	182	810
Amounts reclassified from accumulated other comprehensive (loss) income	1,056	1,096
Net current-period other comprehensive income	1,238	1,906
Ending Balance	(137,649)	(139,838)
Foreign Currency Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(229,746)	(119,151)
Other comprehensive income (loss) before reclassifications	20,476	(83,151)
Amounts reclassified from accumulated other comprehensive (loss) income	0	0
Net current-period other comprehensive income	20,476	(83,151)
Ending Balance	(209,270)	(202,302)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(371,124)	(260,895)
Other comprehensive income (loss) before reclassifications	20,608	(82,098)
Amounts reclassified from accumulated other comprehensive (loss) income	2,586	897
Net current-period other comprehensive income	23,194	(81,201)
Ending Balance	$ (347,930)	$ (342,096)