Shareholders' equity - accumulated other comprehensive income (loss) into income expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 27, 2015	Jun. 28, 2015	Mar. 29, 2015	Dec. 31, 2014	Sep. 28, 2014	Jun. 29, 2014	Mar. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of goods sold									$ 865,287	$ 897,404	$ 857,326
Income from continuing operations before taxes									244,646	220,110	175,730
Taxes on income from continuing operations									7,838	28,650	23,547
Income from continuing operations	$ 90,765	$ 61,571	$ 45,199	$ 39,273	$ 52,133	$ 55,228	$ 48,830	$ 35,269	236,808	191,460	152,183
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total reclassifications, net of tax									4,616	2,235	5,686
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations before taxes									679	(705)	884
Taxes on income from continuing operations									196	(111)	(46)
Income from continuing operations									483	(594)	930
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Commodity Contract
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of goods sold									679	(705)	884
Reclassification out of Accumulated Other Comprehensive Income | Pension and Other Postretirement Benefits Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations before taxes									6,375	4,364	7,195
Taxes on income from continuing operations									(2,242)	(1,535)	(2,439)
Income from continuing operations									4,133	2,829	4,756
Actuarial losses									6,375	4,385	7,211
Prior-service credits									0	(21)	(21)
Transition obligation									$ 0	$ 0	$ 5