Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016	Oct. 01, 2017	Sep. 25, 2016
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 534,703	$ 455,648	$ 1,551,197	$ 1,354,094
Cost of goods sold	239,476	214,046	710,126	630,946
Gross profit	295,227	241,602	841,071	723,148
Selling, general and administrative expenses	163,771	139,797	486,674	419,128
Research and development expenses	21,194	15,067	59,299	42,892
Restructuring charges	(92)	3,027	13,723	12,876
Gain on sale of assets	0	(2,776)	0	(4,173)
(Loss) income from continuing operations before interest, extinguishment of debt and taxes	110,354	86,487	281,375	252,425
Interest, net	20,978	12,773	58,268	38,255
Loss on extinguishment of debt	0	0	5,593	19,261
Income from continuing operations before taxes	89,376	73,714	217,514	194,909
(Benefit) taxes on (loss) income from continuing operations	9,978	7,514	19,404	18,134
Equity in net income of consolidated subsidiaries	0	0	0	0
Income from continuing operations	79,398	66,200	198,110	176,775
Operating loss from discontinued operations	(3,749)	260	(4,597)	(116)
Benefit on loss from discontinued operations	(1,366)	138	(1,675)	(119)
(Loss) income from discontinued operations	(2,383)	122	(2,922)	3
Net income	77,015	66,322	195,188	176,778
Less: Income from continuing operations attributable to noncontrolling interest	0	0	0	464
Net income attributable to common shareholders	77,015	66,322	195,188	176,314
Other comprehensive income	43,845	1,053	163,267	15,806
Comprehensive income attributable to common shareholders	120,860	67,375	358,455	192,120
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(104,024)	(96,220)	(315,085)	(289,247)
Cost of goods sold	(104,088)	(96,246)	(311,977)	(285,547)
Gross profit	64	26	(3,108)	(3,700)
Selling, general and administrative expenses	(126)	(29)	398	470
Research and development expenses	0	0	0	0
Restructuring charges	0	0	0	0
Gain on sale of assets		0		0
(Loss) income from continuing operations before interest, extinguishment of debt and taxes	190	55	(3,506)	(4,170)
Interest, net	0	0	0	0
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	190	55	(3,506)	(4,170)
(Benefit) taxes on (loss) income from continuing operations	6	(72)	(593)	(481)
Equity in net income of consolidated subsidiaries	(174,114)	(156,564)	(487,749)	(455,164)
Income from continuing operations	(173,930)	(156,437)	(490,662)	(458,853)
Operating loss from discontinued operations	0	0	0	0
Benefit on loss from discontinued operations	0	0	0	0
(Loss) income from discontinued operations	0	0	0	0
Net income	(173,930)		(490,662)	(458,853)
Less: Income from continuing operations attributable to noncontrolling interest				0
Net income attributable to common shareholders		(156,437)		(458,853)
Other comprehensive income	(86,482)	(742)	(327,288)	(20,664)
Comprehensive income attributable to common shareholders	(260,412)	(157,179)	(817,950)	(479,517)
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	10,536	11,208	38,523	30,822
Research and development expenses	220	179	719	319
Restructuring charges	0	380	0	380
Gain on sale of assets		(2,707)		(2,707)
(Loss) income from continuing operations before interest, extinguishment of debt and taxes	(10,756)	(9,060)	(39,242)	(28,814)
Interest, net	53,521	41,344	152,268	107,534
Loss on extinguishment of debt			5,593	19,261
Income from continuing operations before taxes	(64,277)	(50,404)	(197,103)	(155,609)
(Benefit) taxes on (loss) income from continuing operations	(30,845)	(18,017)	(83,867)	(56,942)
Equity in net income of consolidated subsidiaries	112,830	98,544	311,346	275,296
Income from continuing operations	79,398	66,157	198,110	176,629
Operating loss from discontinued operations	(3,749)	260	(4,597)	(495)
Benefit on loss from discontinued operations	(1,366)	95	(1,675)	(180)
(Loss) income from discontinued operations	(2,383)	165	(2,922)	(315)
Net income	77,015		195,188	176,314
Less: Income from continuing operations attributable to noncontrolling interest				0
Net income attributable to common shareholders		66,322		176,314
Other comprehensive income	43,845	1,053	163,267	15,806
Comprehensive income attributable to common shareholders	120,860	67,375	358,455	192,120
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	335,051	270,610	989,314	809,951
Cost of goods sold	194,262	163,052	576,465	489,293
Gross profit	140,789	107,558	412,849	320,658
Selling, general and administrative expenses	89,315	80,333	278,529	248,195
Research and development expenses	14,788	8,422	39,568	23,501
Restructuring charges	552	1,712	7,261	7,027
Gain on sale of assets		104		(274)
(Loss) income from continuing operations before interest, extinguishment of debt and taxes	36,134	16,987	87,491	42,209
Interest, net	(33,392)	(29,612)	(96,776)	(72,367)
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	69,526	46,599	184,267	114,576
(Benefit) taxes on (loss) income from continuing operations	23,453	13,166	60,061	39,347
Equity in net income of consolidated subsidiaries	61,027	57,837	175,690	179,342
Income from continuing operations	107,100	91,270	299,896	254,571
Operating loss from discontinued operations	0	0	0	0
Benefit on loss from discontinued operations	0	0	0	0
(Loss) income from discontinued operations	0	0	0	0
Net income	107,100		299,896	254,571
Less: Income from continuing operations attributable to noncontrolling interest				0
Net income attributable to common shareholders		91,270		254,571
Other comprehensive income	30,196	(501)	147,727	8,387
Comprehensive income attributable to common shareholders	137,296	90,769	447,623	262,958
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	303,676	281,258	876,968	833,390
Cost of goods sold	149,302	147,240	445,638	427,200
Gross profit	154,374	134,018	431,330	406,190
Selling, general and administrative expenses	64,046	48,285	169,224	139,641
Research and development expenses	6,186	6,466	19,012	19,072
Restructuring charges	(644)	935	6,462	5,469
Gain on sale of assets		(173)		(1,192)
(Loss) income from continuing operations before interest, extinguishment of debt and taxes	84,786	78,505	236,632	243,200
Interest, net	849	1,041	2,776	3,088
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	83,937	77,464	233,856	240,112
(Benefit) taxes on (loss) income from continuing operations	17,364	12,437	43,803	36,210
Equity in net income of consolidated subsidiaries	257	183	713	526
Income from continuing operations	66,830	65,210	190,766	204,428
Operating loss from discontinued operations	0	0	0	379
Benefit on loss from discontinued operations	0	43	0	61
(Loss) income from discontinued operations	0	(43)	0	318
Net income	66,830		190,766	204,746
Less: Income from continuing operations attributable to noncontrolling interest				464
Net income attributable to common shareholders		65,167		204,282
Other comprehensive income	56,286	1,243	179,561	12,277
Comprehensive income attributable to common shareholders	$ 123,116	$ 66,410	$ 370,327	$ 216,559