Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 609,672	$ 534,703	$ 1,806,768	$ 1,551,197
Cost of goods sold	267,099	239,476	788,147	710,126
Gross profit	342,573	295,227	1,018,621	841,071
Selling, general and administrative expenses	214,894	163,771	660,148	486,674
Research and development expenses	26,365	21,194	78,410	59,299
Restructuring and impairment charges (credits)	19,209	(92)	77,625	13,723
Income from continuing operations before interest, loss on extinguishment of debt and taxes	82,105	110,354	202,438	281,375
Interest, net	26,851	20,978	78,987	58,268
Loss on extinguishment of debt	0	0	0	5,593
Income from continuing operations before taxes	55,254	89,376	123,451	217,514
(Benefit) taxes on (loss) income from continuing operations	(1,286)	9,978	14,532	19,404
Equity in net income of consolidated subsidiaries	0	0	0	0
Income from continuing operations	56,540	79,398	108,919	198,110
Operating loss from discontinued operations	(83)	(3,749)	1,246	(4,597)
Benefit on loss from discontinued operations	(67)	(1,366)	(47)	(1,675)
Income (loss) from discontinued operations	(16)	(2,383)	1,293	(2,922)
Net income	56,524	77,015	110,212	195,188
Other comprehensive income	17,253	43,845	(24,076)	163,267
Comprehensive income	73,777	120,860	86,136	358,455
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(111,299)	(104,024)	(331,214)	(315,085)
Cost of goods sold	(111,411)	(104,088)	(324,994)	(311,977)
Gross profit	112	64	(6,220)	(3,108)
Selling, general and administrative expenses	(22)	(126)	(352)	398
Research and development expenses	0	0	0	0
Restructuring and impairment charges (credits)	0	0	0	0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	134	190	(5,868)	(3,506)
Interest, net	0	0	0	0
Loss on extinguishment of debt				0
Income from continuing operations before taxes	134	190	(5,868)	(3,506)
(Benefit) taxes on (loss) income from continuing operations	13	6	(1,090)	(593)
Equity in net income of consolidated subsidiaries	(149,322)	(158,701)	(347,794)	(442,406)
Income from continuing operations	(149,201)	(158,517)	(352,572)	(445,319)
Operating loss from discontinued operations	0	0	0	0
Benefit on loss from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income	(149,201)	(158,517)	(352,572)	(445,319)
Other comprehensive income	(31,054)	(86,482)	57,242	(327,288)
Comprehensive income	(180,255)	(244,999)	(295,330)	(772,607)
Parent Company
Condensed Income Statements, Captions [Line Items]
Net revenues	0	0	0	0
Cost of goods sold	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expenses	11,347	10,536	32,958	38,523
Research and development expenses	378	220	1,094	719
Restructuring and impairment charges (credits)	0	0	0	0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(11,725)	(10,756)	(34,052)	(39,242)
Interest, net	25,191	29,231	72,120	80,737
Loss on extinguishment of debt				5,593
Income from continuing operations before taxes	(36,916)	(39,987)	(106,172)	(125,572)
(Benefit) taxes on (loss) income from continuing operations	(13,449)	(21,968)	(39,859)	(57,679)
Equity in net income of consolidated subsidiaries	80,007	97,417	176,511	266,003
Income from continuing operations	56,540	79,398	110,198	198,110
Operating loss from discontinued operations	(83)	(3,749)	(33)	(4,597)
Benefit on loss from discontinued operations	(67)	(1,366)	(47)	(1,675)
Income (loss) from discontinued operations	(16)	(2,383)	14	(2,922)
Net income	56,524	77,015	110,212	195,188
Other comprehensive income	17,253	43,845	(24,076)	163,267
Comprehensive income	73,777	120,860	86,136	358,455
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	398,961	335,051	1,169,684	989,314
Cost of goods sold	232,209	194,262	681,300	576,465
Gross profit	166,752	140,789	488,384	412,849
Selling, general and administrative expenses	130,773	89,315	401,252	278,529
Research and development expenses	19,482	14,788	57,668	39,568
Restructuring and impairment charges (credits)	17,128	552	20,581	7,261
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(631)	36,134	8,883	87,491
Interest, net	1,057	(9,102)	5,066	(25,245)
Loss on extinguishment of debt				0
Income from continuing operations before taxes	(1,688)	45,236	3,817	112,736
(Benefit) taxes on (loss) income from continuing operations	(2,562)	14,576	11,347	33,873
Equity in net income of consolidated subsidiaries	68,943	61,027	170,276	175,690
Income from continuing operations	69,817	91,687	162,746	254,553
Operating loss from discontinued operations	0	0	0	0
Benefit on loss from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income	69,817	91,687	162,746	254,553
Other comprehensive income	14,107	30,196	(30,691)	147,727
Comprehensive income	83,924	121,883	132,055	402,280
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	322,010	303,676	968,298	876,968
Cost of goods sold	146,301	149,302	431,841	445,638
Gross profit	175,709	154,374	536,457	431,330
Selling, general and administrative expenses	72,796	64,046	226,290	169,224
Research and development expenses	6,505	6,186	19,648	19,012
Restructuring and impairment charges (credits)	2,081	(644)	57,044	6,462
Income from continuing operations before interest, loss on extinguishment of debt and taxes	94,327	84,786	233,475	236,632
Interest, net	603	849	1,801	2,776
Loss on extinguishment of debt				0
Income from continuing operations before taxes	93,724	83,937	231,674	233,856
(Benefit) taxes on (loss) income from continuing operations	14,712	17,364	44,134	43,803
Equity in net income of consolidated subsidiaries	372	257	1,007	713
Income from continuing operations	79,384	66,830	188,547	190,766
Operating loss from discontinued operations	0	0	1,279	0
Benefit on loss from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	1,279	0
Net income	79,384	66,830	189,826	190,766
Other comprehensive income	16,947	56,286	(26,551)	179,561
Comprehensive income	$ 96,331	$ 123,116	$ 163,275	$ 370,327