Changes in shareholders' equity - Change in accumulated other comprehensive income, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 25, 2016	Sep. 27, 2015	Sep. 25, 2016	Sep. 27, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 2,011,093
Amounts reclassified from accumulated other comprehensive income	$ 1,535	$ 1,967	6,312	$ 4,267
Reclassification related to acquisition of noncontrolling interest			(9,231)
Ending Balance	2,169,922		2,169,922
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(2,491)	0
Other comprehensive income (loss) before reclassifications			(2,255)	(2,599)
Amounts reclassified from accumulated other comprehensive income	348	947	3,016	1,110
Net current-period other comprehensive income			761	(1,489)
Reclassification related to acquisition of noncontrolling interest			0
Ending Balance	(1,730)	(1,489)	(1,730)	(1,489)
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			618	465
Amounts reclassified from accumulated other comprehensive income	1,187	1,020	3,296	3,157
Net current-period other comprehensive income			3,914	3,622
Reclassification related to acquisition of noncontrolling interest			0
Ending Balance	(134,973)	(138,122)	(134,973)	(138,122)
Foreign Currency Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(229,746)	(119,151)
Other comprehensive income (loss) before reclassifications			11,131	(91,137)
Amounts reclassified from accumulated other comprehensive income			0	0
Net current-period other comprehensive income			11,131	(91,137)
Reclassification related to acquisition of noncontrolling interest			(832)
Ending Balance	(219,447)	(210,288)	(219,447)	(210,288)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(371,124)	(260,895)
Other comprehensive income (loss) before reclassifications			9,494	(93,271)
Amounts reclassified from accumulated other comprehensive income			6,312	4,267
Net current-period other comprehensive income			15,806	(89,004)
Reclassification related to acquisition of noncontrolling interest			(832)
Ending Balance	$ (356,150)	$ (349,899)	$ (356,150)	$ (349,899)

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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The change in other comprehensive income during the reporting period, net of tax, for an item that is not separately disclosed.

+ 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.

+ References

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