Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 02, 2017	Mar. 27, 2016
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 487,881	$ 424,893
Cost of goods sold	232,321	199,746
Gross profit	255,560	225,147
Selling, general and administrative expenses	163,969	136,348
Research and development expenses	17,827	12,353
Restructuring charges	12,945	9,968
Gain on sale of assets	0	(1,019)
Income from continuing operations before interest, loss on extinguishment of debt and taxes	60,819	67,497
Interest, net	17,557	13,704
Loss on extinguishment of debt	5,582	0
Income from continuing operations before taxes	37,680	53,793
(Benefit) taxes on (loss) income from continuing operations	(2,669)	2,613
Equity in net income of consolidated subsidiaries	0	0
Income from continuing operations	40,349	51,180
Operating income from discontinued operations	(282)	(382)
Tax on income from discontinued operations	(103)	(70)
Loss from discontinued operations	(179)	(312)
Net income	40,170	50,868
Less: Income from continuing operations attributable to noncontrolling interest	0	179
Net income attributable to common shareholders	40,170	50,689
Other comprehensive income (loss) attributable to common shareholders	49,600	23,194
Comprehensive income attributable to common shareholders	89,770	73,883
Reportable Legal Entities | Parent Company
Condensed Income Statements, Captions [Line Items]
Net revenues	0	0
Cost of goods sold	0	0
Gross profit	0	0
Selling, general and administrative expenses	20,519	9,329
Research and development expenses	235	0
Restructuring charges	0	0
Gain on sale of assets		0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(20,754)	(9,329)
Interest, net	47,674	33,044
Loss on extinguishment of debt	5,582
Income from continuing operations before taxes	(74,010)	(42,373)
(Benefit) taxes on (loss) income from continuing operations	(29,907)	(15,848)
Equity in net income of consolidated subsidiaries	84,452	77,457
Income from continuing operations	40,349	50,932
Operating income from discontinued operations	(282)	(382)
Tax on income from discontinued operations	(103)	(139)
Loss from discontinued operations	(179)	(243)
Net income	40,170	50,689
Less: Income from continuing operations attributable to noncontrolling interest		0
Net income attributable to common shareholders		50,689
Other comprehensive income (loss) attributable to common shareholders	49,600	23,194
Comprehensive income attributable to common shareholders	89,770	73,883
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	315,643	258,911
Cost of goods sold	192,001	155,541
Gross profit	123,642	103,370
Selling, general and administrative expenses	94,043	81,477
Research and development expenses	11,186	6,435
Restructuring charges	5,374	4,758
Gain on sale of assets		0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	13,039	10,700
Interest, net	(30,963)	(20,318)
Loss on extinguishment of debt	0
Income from continuing operations before taxes	44,002	31,018
(Benefit) taxes on (loss) income from continuing operations	14,485	11,677
Equity in net income of consolidated subsidiaries	55,802	57,900
Income from continuing operations	85,319	77,241
Operating income from discontinued operations	0	0
Tax on income from discontinued operations	0	0
Loss from discontinued operations	0	0
Net income	85,319	77,241
Less: Income from continuing operations attributable to noncontrolling interest		0
Net income attributable to common shareholders		77,241
Other comprehensive income (loss) attributable to common shareholders	49,404	18,573
Comprehensive income attributable to common shareholders	134,723	95,814
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	276,315	261,348
Cost of goods sold	143,896	132,963
Gross profit	132,419	128,385
Selling, general and administrative expenses	48,844	45,059
Research and development expenses	6,406	5,918
Restructuring charges	7,571	5,210
Gain on sale of assets		(1,019)
Income from continuing operations before interest, loss on extinguishment of debt and taxes	69,598	73,217
Interest, net	846	978
Loss on extinguishment of debt	0
Income from continuing operations before taxes	68,752	72,239
(Benefit) taxes on (loss) income from continuing operations	12,229	7,864
Equity in net income of consolidated subsidiaries	216	168
Income from continuing operations	56,739	64,543
Operating income from discontinued operations	0	0
Tax on income from discontinued operations	0	69
Loss from discontinued operations	0	(69)
Net income	56,739	64,474
Less: Income from continuing operations attributable to noncontrolling interest		179
Net income attributable to common shareholders		64,295
Other comprehensive income (loss) attributable to common shareholders	53,901	22,412
Comprehensive income attributable to common shareholders	110,640	86,707
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(104,077)	(95,366)
Cost of goods sold	(103,576)	(88,758)
Gross profit	(501)	(6,608)
Selling, general and administrative expenses	563	483
Research and development expenses	0	0
Restructuring charges	0	0
Gain on sale of assets		0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(1,064)	(7,091)
Interest, net	0	0
Loss on extinguishment of debt	0
Income from continuing operations before taxes	(1,064)	(7,091)
(Benefit) taxes on (loss) income from continuing operations	524	(1,080)
Equity in net income of consolidated subsidiaries	(140,470)	(135,525)
Income from continuing operations	(142,058)	(141,536)
Operating income from discontinued operations	0	0
Tax on income from discontinued operations	0	0
Loss from discontinued operations	0	0
Net income	(142,058)	(141,536)
Less: Income from continuing operations attributable to noncontrolling interest		0
Net income attributable to common shareholders		(141,536)
Other comprehensive income (loss) attributable to common shareholders	(103,305)	(40,985)
Comprehensive income attributable to common shareholders	$ (245,363)	$ (182,521)