Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2017	Jun. 26, 2016	Jul. 02, 2017	Jun. 26, 2016
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 528,613	$ 473,553	$ 1,016,494	$ 898,446
Cost of goods sold	238,329	217,154	470,650	416,900
Gross profit	290,284	256,399	545,844	481,546
Selling, general and administrative expenses	158,934	142,983	322,903	279,331
Research and development expenses	20,278	15,472	38,105	27,825
Restructuring charges	870	(119)	13,815	9,849
Gain on sale of assets	0	(378)	0	(1,397)
Income from continuing operations before interest, loss on extinguishment of debt and taxes	110,202	98,441	171,021	165,938
Interest, net	19,733	11,778	37,290	25,482
Loss on extinguishment of debt	11	19,261	5,593	19,261
Income from continuing operations before taxes	90,458	67,402	128,138	121,195
(Benefit) taxes on (loss) income from continuing operations	12,095	8,007	9,426	10,620
Equity in net income of consolidated subsidiaries	0	0	0	0
Income from continuing operations	78,363	59,395	118,712	110,575
Operating loss from discontinued operations	(566)	6	(848)	(376)
Benefit on loss from discontinued operations	(206)	(187)	(309)	(257)
Income (loss) from discontinued operations	(360)	193	(539)	(119)
Net income	78,003	59,588	118,173	110,456
Less: Income from continuing operations attributable to noncontrolling interest	0	285	0	464
Net income	78,003	59,303	118,173	109,992
Other comprehensive income	69,822	(8,441)	119,422	14,753
Comprehensive income attributable to common shareholders	147,825	50,862	237,595	124,745
Reportable Legal Entities | 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	7,468	10,285	27,987	19,614
Research and development expenses	264	140	499	140
Restructuring charges	0	0	0	0
Gain on sale of assets		0		0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(7,732)	(10,425)	(28,486)	(19,754)
Interest, net	51,073	33,146	98,747	66,190
Loss on extinguishment of debt	11	19,261	5,593	19,261
Income from continuing operations before taxes	(58,816)	(62,832)	(132,826)	(105,205)
(Benefit) taxes on (loss) income from continuing operations	(23,115)	(23,077)	(53,022)	(38,925)
Equity in net income of consolidated subsidiaries	114,064	99,295	198,516	176,752
Income from continuing operations	78,363	59,540	118,712	110,472
Operating loss from discontinued operations	(566)	(373)	(848)	(755)
Benefit on loss from discontinued operations	(206)	(136)	(309)	(275)
Income (loss) from discontinued operations	(360)	(237)	(539)	(480)
Net income	78,003	59,303	118,173	109,992
Less: Income from continuing operations attributable to noncontrolling interest		0		0
Net income		59,303		109,992
Other comprehensive income	69,822	(8,441)	119,422	14,753
Comprehensive income attributable to common shareholders	147,825	50,862	237,595	124,745
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	338,620	280,430	654,263	539,341
Cost of goods sold	190,202	170,700	382,203	326,241
Gross profit	148,418	109,730	272,060	213,100
Selling, general and administrative expenses	95,171	86,385	189,214	167,862
Research and development expenses	13,594	8,644	24,780	15,079
Restructuring charges	1,335	557	6,709	5,315
Gain on sale of assets		(378)		(378)
Income from continuing operations before interest, loss on extinguishment of debt and taxes	38,318	14,522	51,357	25,222
Interest, net	(32,421)	(22,437)	(63,384)	(42,755)
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	70,739	36,959	114,741	67,977
(Benefit) taxes on (loss) income from continuing operations	22,123	14,504	36,608	26,181
Equity in net income of consolidated subsidiaries	58,861	63,605	114,663	121,505
Income from continuing operations	107,477	86,060	192,796	163,301
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	107,477	86,060	192,796	163,301
Less: Income from continuing operations attributable to noncontrolling interest		0		0
Net income		86,060		163,301
Other comprehensive income	68,127	(9,685)	117,531	8,888
Comprehensive income attributable to common shareholders	175,604	76,375	310,327	172,189
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	296,977	290,784	573,292	552,132
Cost of goods sold	152,440	146,997	296,336	279,960
Gross profit	144,537	143,787	276,956	272,172
Selling, general and administrative expenses	56,334	46,297	105,178	91,356
Research and development expenses	6,420	6,688	12,826	12,606
Restructuring charges	(465)	(676)	7,106	4,534
Gain on sale of assets		0		(1,019)
Income from continuing operations before interest, loss on extinguishment of debt and taxes	82,248	91,478	151,846	164,695
Interest, net	1,081	1,069	1,927	2,047
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	81,167	90,409	149,919	162,648
(Benefit) taxes on (loss) income from continuing operations	14,210	15,909	26,439	23,773
Equity in net income of consolidated subsidiaries	240	175	456	343
Income from continuing operations	67,197	74,675	123,936	139,218
Operating loss from discontinued operations	0	379	0	379
Benefit on loss from discontinued operations	0	(51)	0	18
Income (loss) from discontinued operations	0	430	0	361
Net income	67,197	75,105	123,936	139,579
Less: Income from continuing operations attributable to noncontrolling interest		285		464
Net income		74,820		139,115
Other comprehensive income	69,374	(11,378)	123,275	11,034
Comprehensive income attributable to common shareholders	136,571	63,442	247,211	150,149
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(106,984)	(97,661)	(211,061)	(193,027)
Cost of goods sold	(104,313)	(100,543)	(207,889)	(189,301)
Gross profit	(2,671)	2,882	(3,172)	(3,726)
Selling, general and administrative expenses	(39)	16	524	499
Research and development expenses	0	0	0	0
Restructuring charges	0	0	0	0
Gain on sale of assets		0		0
Income from continuing operations before interest, loss on extinguishment of debt and taxes	(2,632)	2,866	(3,696)	(4,225)
Interest, net	0	0	0	0
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	(2,632)	2,866	(3,696)	(4,225)
(Benefit) taxes on (loss) income from continuing operations	(1,123)	671	(599)	(409)
Equity in net income of consolidated subsidiaries	(173,165)	(163,075)	(313,635)	(298,600)
Income from continuing operations	(174,674)	(160,880)	(316,732)	(302,416)
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	(174,674)	(160,880)	(316,732)	(302,416)
Less: Income from continuing operations attributable to noncontrolling interest		0		0
Net income		(160,880)		(302,416)
Other comprehensive income	(137,501)	21,063	(240,806)	(19,922)
Comprehensive income attributable to common shareholders	$ (312,175)	$ (139,817)	$ (557,538)	$ (322,338)