Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jul. 01, 2018	Apr. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 652,507		$ 609,866		$ 1,266,091	$ 1,197,096
Cost of goods sold	279,583		265,088		548,425	521,048
Gross profit	372,924		344,778		717,666	676,048
Selling, general and administrative expenses	236,186		229,917		463,879	445,254
Research and development expenses	27,595		26,018		54,745	52,045
Restructuring and impairment charges	1,685		55,353		19,080	58,416
Gain on sale of assets	0		0		(2,739)	0
Income from continuing operations before interest and taxes	107,458		33,490		182,701	120,333
Interest, net	20,286		26,466		42,639	52,136
Income from continuing operations before taxes	87,172		7,024		140,062	68,197
(Benefit) taxes on (loss) income from continuing operations	3,844		9,576		14,816	15,818
Equity in net income of consolidated subsidiaries	0		0		0	0
Income from continuing operations	83,328		(2,552)		125,246	52,379
Operating loss from discontinued operations	61		94		(1,282)	1,329
Benefit on loss from discontinued operations	14		38		(308)	20
Income (loss) from discontinued operations	47		56		(974)	1,309
Net income (loss)	83,375	$ 40,897	(2,496)	$ 56,184	124,272	53,688
Other comprehensive income	14,782		(124,019)		15,178	(41,329)
Comprehensive income	98,157		(126,515)		139,450	12,359
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(114,578)		(107,717)		(237,130)	(219,915)
Cost of goods sold	(116,796)		(109,931)		(230,028)	(213,583)
Gross profit	2,218		2,214		(7,102)	(6,332)
Selling, general and administrative expenses	(266)		199		92	(330)
Research and development expenses	0		0		0	0
Restructuring and impairment charges	0		0		0	0
Gain on sale of assets					0
Income from continuing operations before interest and taxes	2,484		2,015		(7,194)	(6,002)
Interest, net	0		0		0	0
Income from continuing operations before taxes	2,484		2,015		(7,194)	(6,002)
(Benefit) taxes on (loss) income from continuing operations	202		63		(1,233)	(1,103)
Equity in net income of consolidated subsidiaries	(166,018)		(35,462)		(262,826)	(175,746)
Income from continuing operations	(163,736)		(33,510)		(268,787)	(180,645)
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 (loss)	(163,736)		(33,510)		(268,787)	(180,645)
Other comprehensive income	(36,564)		245,642		(30,069)	88,296
Comprehensive income	(200,300)		212,132		(298,856)	(92,349)
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	14,312		12,430		30,479	21,611
Research and development expenses	596		489		1,080	716
Restructuring and impairment charges	0		0		0	0
Gain on sale of assets					0
Income from continuing operations before interest and taxes	(14,908)		(12,919)		(31,559)	(22,327)
Interest, net	29,350		24,788		33,415	46,929
Income from continuing operations before taxes	(44,258)		(37,707)		(64,974)	(69,256)
(Benefit) taxes on (loss) income from continuing operations	(19,519)		(13,218)		(28,391)	(26,410)
Equity in net income of consolidated subsidiaries	108,067		21,937		161,829	96,504
Income from continuing operations	83,328		(2,552)		125,246	53,658
Operating loss from discontinued operations	61		94		(1,282)	50
Benefit on loss from discontinued operations	14		38		(308)	20
Income (loss) from discontinued operations	47		56		(974)	30
Net income (loss)	83,375		(2,496)		124,272	53,688
Other comprehensive income	14,782		(124,019)		15,178	(41,329)
Comprehensive income	98,157		(126,515)		139,450	12,359
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	439,489		391,304		854,632	770,723
Cost of goods sold	244,956		231,487		479,173	449,091
Gross profit	194,533		159,817		375,459	321,632
Selling, general and administrative expenses	141,628		139,549		273,327	270,218
Research and development expenses	20,331		18,818		40,452	38,186
Restructuring and impairment charges	108		2,545		6,081	3,453
Gain on sale of assets					0
Income from continuing operations before interest and taxes	32,466		(1,095)		55,599	9,775
Interest, net	(23,439)		(13,966)		(21,845)	(26,015)
Income from continuing operations before taxes	55,905		12,871		77,444	35,790
(Benefit) taxes on (loss) income from continuing operations	15,681		11,272		27,250	21,468
Equity in net income of consolidated subsidiaries	57,951		13,183		100,997	78,607
Income from continuing operations	98,175		14,782		151,191	92,929
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 (loss)	98,175		14,782		151,191	92,929
Other comprehensive income	17,107		(114,917)		15,606	(44,798)
Comprehensive income	115,282		(100,135)		166,797	48,131
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	327,596		326,279		648,589	646,288
Cost of goods sold	151,423		143,532		299,280	285,540
Gross profit	176,173		182,747		349,309	360,748
Selling, general and administrative expenses	80,512		77,739		159,981	153,755
Research and development expenses	6,668		6,711		13,213	13,143
Restructuring and impairment charges	1,577		52,808		12,999	54,963
Gain on sale of assets					(2,739)
Income from continuing operations before interest and taxes	87,416		45,489		165,855	138,887
Interest, net	14,375		15,644		31,069	31,222
Income from continuing operations before taxes	73,041		29,845		134,786	107,665
(Benefit) taxes on (loss) income from continuing operations	7,480		11,459		17,190	21,863
Equity in net income of consolidated subsidiaries	0		342		0	635
Income from continuing operations	65,561		18,728		117,596	86,437
Operating loss from discontinued operations	0		0		0	1,279
Benefit on loss from discontinued operations	0		0		0	0
Income (loss) from discontinued operations	0		0		0	1,279
Net income (loss)	65,561		18,728		117,596	87,716
Other comprehensive income	19,457		(130,725)		14,463	(43,498)
Comprehensive income	$ 85,018		$ (111,997)		$ 132,059	$ 44,218