Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2016	Sep. 27, 2015	Sep. 25, 2016	Sep. 27, 2015
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 455,648	$ 443,714	$ 1,354,094	$ 1,325,189
Cost of goods sold	214,046	215,501	630,946	641,102
Gross profit	241,602	228,213	723,148	684,087
Selling, general and administrative expenses	139,797	138,840	419,128	420,765
Research and development expenses	15,067	12,571	42,892	38,898
Restructuring charges	3,027	660	12,876	5,688
Gain on sale of assets	(2,776)	(408)	(4,173)	(408)
Income from continuing operations before interest, extinguishment of debt and taxes	86,487	76,550	252,425	219,144
Interest, net	12,773	14,176	38,255	47,232
Loss on extinguishment of debt	0	0	19,261	10,454
Income from continuing operations before taxes	73,714	62,374	194,909	161,458
(Benefit) taxes on (loss) income from continuing operations	7,514	803	18,134	15,415
Equity in net income of consolidated subsidiaries	0	0	0	0
Income from continuing operations	66,200	61,571	176,775	146,043
Operating income from discontinued operations	260	(788)	(116)	(1,432)
Tax on income from discontinued operations	138	(69)	(119)	180
Income (loss) from discontinued operations	122	(719)	3	(1,612)
Net income	66,322	60,852	176,778	144,431
Less: Income from continuing operations attributable to noncontrolling interest	0	28	464	692
Net income attributable to common shareholders	66,322	60,824	176,314	143,739
Other comprehensive income (loss) attributable to common shareholders	1,053	(28,789)	15,806	(89,004)
Comprehensive income attributable to common shareholders	67,375	32,035	192,120	54,735
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	11,208	9,891	30,822	30,006
Research and development expenses	179	0	319	0
Restructuring charges	380	0	380	0
Gain on sale of assets	(2,707)	0	(2,707)	0
Income from continuing operations before interest, extinguishment of debt and taxes	(9,060)	(9,891)	(28,814)	(30,006)
Interest, net	41,344	32,439	107,534	100,157
Loss on extinguishment of debt			19,261	10,454
Income from continuing operations before taxes	(50,404)	(42,330)	(155,609)	(140,617)
(Benefit) taxes on (loss) income from continuing operations	(18,017)	(15,102)	(56,942)	(48,336)
Equity in net income of consolidated subsidiaries	98,544	88,728	275,296	237,512
Income from continuing operations	66,157	61,500	176,629	145,231
Operating income from discontinued operations	260	(784)	(495)	(1,432)
Tax on income from discontinued operations	95	(108)	(180)	60
Income (loss) from discontinued operations	165	(676)	(315)	(1,492)
Net income		60,824	176,314	143,739
Less: Income from continuing operations attributable to noncontrolling interest		0	0	0
Net income attributable to common shareholders	66,322	60,824	176,314	143,739
Other comprehensive income (loss) attributable to common shareholders	1,053	(28,789)	15,806	(89,004)
Comprehensive income attributable to common shareholders	67,375	32,035	192,120	54,735
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	270,610	269,620	809,951	803,484
Cost of goods sold	163,052	159,567	489,293	476,611
Gross profit	107,558	110,053	320,658	326,873
Selling, general and administrative expenses	80,333	82,372	248,195	249,484
Research and development expenses	8,422	6,006	23,501	22,027
Restructuring charges	1,712	602	7,027	4,932
Gain on sale of assets	104	0	(274)	0
Income from continuing operations before interest, extinguishment of debt and taxes	16,987	21,073	42,209	50,430
Interest, net	(29,612)	(19,457)	(72,367)	(56,591)
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	46,599	40,530	114,576	107,021
(Benefit) taxes on (loss) income from continuing operations	13,166	7,582	39,347	33,491
Equity in net income of consolidated subsidiaries	57,837	49,885	179,342	161,539
Income from continuing operations	91,270	82,833	254,571	235,069
Operating income from discontinued operations	0	0	0	0
Tax on income from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income		82,833	254,571	235,069
Less: Income from continuing operations attributable to noncontrolling interest		0	0	0
Net income attributable to common shareholders	91,270	82,833	254,571	235,069
Other comprehensive income (loss) attributable to common shareholders	(501)	(32,855)	8,387	(94,601)
Comprehensive income attributable to common shareholders	90,769	49,978	262,958	140,468
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net revenues	281,258	270,084	833,390	805,243
Cost of goods sold	147,240	153,207	427,200	443,180
Gross profit	134,018	116,877	406,190	362,063
Selling, general and administrative expenses	48,285	46,471	139,641	141,252
Research and development expenses	6,466	6,565	19,072	16,871
Restructuring charges	935	58	5,469	756
Gain on sale of assets	(173)	(408)	(1,192)	(408)
Income from continuing operations before interest, extinguishment of debt and taxes	78,505	64,191	243,200	203,592
Interest, net	1,041	1,194	3,088	3,666
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	77,464	62,997	240,112	199,926
(Benefit) taxes on (loss) income from continuing operations	12,437	8,053	36,210	31,260
Equity in net income of consolidated subsidiaries	183	211	526	430
Income from continuing operations	65,210	55,155	204,428	169,096
Operating income from discontinued operations	0	(4)	379	0
Tax on income from discontinued operations	43	39	61	120
Income (loss) from discontinued operations	(43)	(43)	318	(120)
Net income		55,112	204,746	168,976
Less: Income from continuing operations attributable to noncontrolling interest		28	464	692
Net income attributable to common shareholders	65,167	55,084	204,282	168,284
Other comprehensive income (loss) attributable to common shareholders	1,243	(26,073)	12,277	(101,461)
Comprehensive income attributable to common shareholders	66,410	29,011	216,559	66,823
Consolidation, Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(96,220)	(95,990)	(289,247)	(283,538)
Cost of goods sold	(96,246)	(97,273)	(285,547)	(278,689)
Gross profit	26	1,283	(3,700)	(4,849)
Selling, general and administrative expenses	(29)	106	470	23
Research and development expenses	0	0	0	0
Restructuring charges	0	0	0	0
Gain on sale of assets	0	0	0	0
Income from continuing operations before interest, extinguishment of debt and taxes	55	1,177	(4,170)	(4,872)
Interest, net	0	0	0	0
Loss on extinguishment of debt			0	0
Income from continuing operations before taxes	55	1,177	(4,170)	(4,872)
(Benefit) taxes on (loss) income from continuing operations	(72)	270	(481)	(1,000)
Equity in net income of consolidated subsidiaries	(156,564)	(138,824)	(455,164)	(399,481)
Income from continuing operations	(156,437)	(137,917)	(458,853)	(403,353)
Operating income from discontinued operations	0	0	0	0
Tax on income from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income		(137,917)	(458,853)	(403,353)
Less: Income from continuing operations attributable to noncontrolling interest		0	0	0
Net income attributable to common shareholders	(156,437)	(137,917)	(458,853)	(403,353)
Other comprehensive income (loss) attributable to common shareholders	(742)	58,928	(20,664)	196,062
Comprehensive income attributable to common shareholders	$ (157,179)	$ (78,989)	$ (479,517)	$ (207,291)