Shareholders' equity - Change in accumulated other comprehensive income, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 01, 2017	Sep. 25, 2016	Oct. 01, 2017	Sep. 25, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 2,137,517
Other comprehensive income (loss) before reclassifications			158,345	$ 9,494
Amounts reclassified from accumulated other comprehensive income	$ 182	$ 1,535	4,922	6,312
Net current-period other comprehensive income			163,267	15,806
Reclassification related to acquisition of noncontrolling interest				(832)
Ending Balance	2,472,477		2,472,477
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(2,424)	(2,491)
Other comprehensive income (loss) before reclassifications			3,383	(2,255)
Amounts reclassified from accumulated other comprehensive income			1,535	3,016
Net current-period other comprehensive income			4,918	761
Ending Balance	2,494	(1,730)	2,494	(1,730)
Pension and Other Postretirement Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(136,596)	(138,887)
Other comprehensive income (loss) before reclassifications			(1,050)	618
Amounts reclassified from accumulated other comprehensive income	1,124	1,187	3,387	3,296
Net current-period other comprehensive income			2,337	3,914
Ending Balance	(134,259)	(134,973)	(134,259)	(134,973)
Foreign Currency Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(299,697)	(229,746)
Other comprehensive income (loss) before reclassifications			156,012	11,131
Amounts reclassified from accumulated other comprehensive income			0	0
Net current-period other comprehensive income			156,012	11,131
Reclassification related to acquisition of noncontrolling interest				(832)
Ending Balance	(143,685)	(219,447)	(143,685)	(219,447)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(438,717)	(371,124)
Ending Balance	$ (275,450)	$ (356,150)	$ (275,450)	$ (356,150)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

The amount of the reduction or elimination during the period of a noncontrolling interest resulting from the parent's loss of control and deconsolidation of the entity in which one or more outside parties had a noncontrolling interest.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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.

+ References

No definition available.

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

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- Definition

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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