Shareholders' equity - Change in accumulated other comprehensive income, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,664,844	$ 2,433,981	$ 2,539,978	$ 2,430,531
Amounts reclassified from accumulated other comprehensive income	(3,002)	1,214	(7,331)	3,111
Ending Balance	2,852,976	2,507,065	2,852,976	2,507,065
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			807	340
Other comprehensive income (loss) before reclassifications			646	2,816
Amounts reclassified from accumulated other comprehensive income			(748)	(873)
Net current-period other comprehensive (loss) income			(102)	1,943
Ending Balance	705	2,283	705	2,283
Pension and Other Postretirement Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(131,380)	(138,808)
Other comprehensive income (loss) before reclassifications			215	127
Amounts reclassified from accumulated other comprehensive income	1,332	1,276	4,033	3,984
Net current-period other comprehensive (loss) income			4,248	4,111
Ending Balance	(127,132)	(134,697)	(127,132)	(134,697)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(210,512)	(126,623)
Other comprehensive income (loss) before reclassifications			(27,562)	(30,130)
Amounts reclassified from accumulated other comprehensive income			0	0
Net current-period other comprehensive (loss) income			(27,562)	(30,130)
Ending Balance	(238,074)	(156,753)	(238,074)	(156,753)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(325,907)	(306,420)	(341,085)	(265,091)
Other comprehensive income (loss) before reclassifications			(26,701)	(27,187)
Amounts reclassified from accumulated other comprehensive income			3,285	3,111
Net current-period other comprehensive (loss) income			(23,416)	(24,076)
Ending Balance	$ (364,501)	$ (289,167)	$ (364,501)	$ (289,167)

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount of increase (decrease) in other comprehensive income, after tax, from changes classified as other.

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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