Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2018	Apr. 02, 2017
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 587,230	$ 487,881
Cost of goods sold	255,960	232,321
Gross profit	331,270	255,560
Selling, general and administrative expenses	215,337	163,969
Research and development expenses	26,027	17,827
Restructuring charges	3,063	12,945
Income from continuing operations before interest, loss on extinguishment of debt and taxes	86,843	60,819
Interest, net	25,670	17,557
Loss on extinguishment of debt	0	5,582
Income from continuing operations before taxes	61,173	37,680
(Benefit) taxes on (loss) income from continuing operations	6,242	(2,669)
Equity in net income of consolidated subsidiaries	0	0
Income from continuing operations	54,931	40,349
Operating loss from discontinued operations	1,235	(282)
Benefit on loss from discontinued operations	(18)	(103)
Income (loss) from discontinued operations	1,253	(179)
Net income	56,184	40,170
Other comprehensive income	82,690	49,600
Comprehensive income	138,874	89,770
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(112,198)	(104,077)
Cost of goods sold	(103,652)	(103,576)
Gross profit	(8,546)	(501)
Selling, general and administrative expenses	(529)	563
Research and development expenses	0	0
Restructuring charges	0	0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(8,017)	(1,064)
Interest, net	0	0
Loss on extinguishment of debt		0
Income from continuing operations before taxes	(8,017)	(1,064)
(Benefit) taxes on (loss) income from continuing operations	(1,166)	524
Equity in net income of consolidated subsidiaries	(151,736)	(125,643)
Income from continuing operations	(158,587)	(127,231)
Operating loss from discontinued operations	0	0
Benefit on loss from discontinued operations	0	0
Income (loss) from discontinued operations	0	0
Net income	(158,587)	(127,231)
Other comprehensive income	(157,346)	(103,305)
Comprehensive income	(315,933)	(230,536)
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	9,181	20,519
Research and development expenses	227	235
Restructuring charges	0	0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(9,408)	(20,754)
Interest, net	22,141	24,273
Loss on extinguishment of debt		5,582
Income from continuing operations before taxes	(31,549)	(50,609)
(Benefit) taxes on (loss) income from continuing operations	(13,192)	(21,333)
Equity in net income of consolidated subsidiaries	74,567	69,625
Income from continuing operations	56,210	40,349
Operating loss from discontinued operations	(44)	(282)
Benefit on loss from discontinued operations	(18)	(103)
Income (loss) from discontinued operations	(26)	(179)
Net income	56,184	40,170
Other comprehensive income	82,690	49,600
Comprehensive income	138,874	89,770
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	379,419	315,643
Cost of goods sold	217,604	192,001
Gross profit	161,815	123,642
Selling, general and administrative expenses	130,914	94,043
Research and development expenses	19,368	11,186
Restructuring charges	908	5,374
Income from continuing operations before interest, loss on extinguishment of debt and taxes	10,625	13,039
Interest, net	2,931	(7,562)
Loss on extinguishment of debt		0
Income from continuing operations before taxes	7,694	20,601
(Benefit) taxes on (loss) income from continuing operations	6,423	5,911
Equity in net income of consolidated subsidiaries	76,876	55,802
Income from continuing operations	78,147	70,492
Operating loss from discontinued operations	0	0
Benefit on loss from discontinued operations	0	0
Income (loss) from discontinued operations	0	0
Net income	78,147	70,492
Other comprehensive income	70,119	49,404
Comprehensive income	148,266	119,896
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	320,009	276,315
Cost of goods sold	142,008	143,896
Gross profit	178,001	132,419
Selling, general and administrative expenses	75,771	48,844
Research and development expenses	6,432	6,406
Restructuring charges	2,155	7,571
Income from continuing operations before interest, loss on extinguishment of debt and taxes	93,643	69,598
Interest, net	598	846
Loss on extinguishment of debt		0
Income from continuing operations before taxes	93,045	68,752
(Benefit) taxes on (loss) income from continuing operations	14,177	12,229
Equity in net income of consolidated subsidiaries	293	216
Income from continuing operations	79,161	56,739
Operating loss from discontinued operations	1,279	0
Benefit on loss from discontinued operations	0	0
Income (loss) from discontinued operations	1,279	0
Net income	80,440	56,739
Other comprehensive income	87,227	53,901
Comprehensive income	$ 167,667	$ 110,640