Condensed consolidating guarantor financial information - Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2016	Jun. 28, 2015	Jun. 26, 2016	Jun. 28, 2015
Condensed Income Statements, Captions [Line Items]
Net revenues	$ 473,553	$ 452,045	$ 898,446	$ 881,475
Cost of goods sold	217,154	218,808	416,900	425,601
Gross profit	256,399	233,237	481,546	455,874
Selling, general and administrative expenses	142,983	142,228	279,331	281,925
Research and development expenses	15,472	13,443	27,825	26,327
Restructuring charges	(119)	580	9,849	5,028
Gain on sale of assets	(378)	0	(1,397)	0
Income from continuing operations before interest and taxes	98,441	76,986	165,938	142,594
Interest, net	11,778	16,053	25,482	33,056
Loss on extinguishment of debt	19,261	10,454	19,261	10,454
Income from continuing operations before taxes	67,402	50,479	121,195	99,084
(Benefit) taxes on (loss) income from continuing operations	8,007	5,280	10,620	14,612
Equity in net income of consolidated subsidiaries	0	0	0	0
Income from continuing operations	59,395	45,199	110,575	84,472
Operating (loss) income from discontinued operations	6	(145)	(376)	(644)
Tax (benefit) on (loss) income from discontinued operations	(187)	45	(257)	249
Income (loss) from discontinued operations	193	(190)	(119)	(893)
Net income	59,588	45,009	110,456	83,579
Less: Income from continuing operations attributable to noncontrolling interest	285	446	464	664
Net income attributable to common shareholders	59,303	44,563	109,992	82,915
Other comprehensive loss attributable to common shareholders	(8,441)	20,986	14,753	(60,215)
Comprehensive income attributable to common shareholders	50,862	65,549	124,745	22,700
Consolidation, Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenues	(97,661)	(93,916)	(193,027)	(187,548)
Cost of goods sold	(100,543)	(92,265)	(189,301)	(181,416)
Gross profit	2,882	(1,651)	(3,726)	(6,132)
Selling, general and administrative expenses	16	(243)	499	(83)
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 and taxes	2,866	(1,408)	(4,225)	(6,049)
Interest, net	0	0	0	0
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	2,866	(1,408)	(4,225)	(6,049)
(Benefit) taxes on (loss) income from continuing operations	671	(159)	(409)	(1,270)
Equity in net income of consolidated subsidiaries	(163,075)	(131,332)	(298,600)	(260,657)
Income from continuing operations	(160,880)	(132,581)	(302,416)	(265,436)
Operating (loss) income from discontinued operations	0	0	0	0
Tax (benefit) on (loss) income from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income	(160,880)	(132,581)	(302,416)	(265,436)
Less: Income from continuing operations attributable to noncontrolling interest	0	0	0	0
Net income attributable to common shareholders	(160,880)	(132,581)	(302,416)	(265,436)
Other comprehensive loss attributable to common shareholders	21,063	(69,355)	(19,922)	137,134
Comprehensive income attributable to common shareholders	(139,817)	(201,936)	(322,338)	(128,302)
Parent Company | Reportable Legal Entities
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	10,285	8,663	19,614	20,115
Research and development expenses	140	0	140	0
Restructuring charges	0	0	0	0
Gain on sale of assets	0		0
Income from continuing operations before interest and taxes	(10,425)	(8,663)	(19,754)	(20,115)
Interest, net	33,146	33,358	66,190	67,718
Loss on extinguishment of debt	19,261	10,454	19,261	10,454
Income from continuing operations before taxes	(62,832)	(52,475)	(105,205)	(98,287)
(Benefit) taxes on (loss) income from continuing operations	(23,077)	(17,941)	(38,925)	(33,234)
Equity in net income of consolidated subsidiaries	99,295	79,246	176,752	148,784
Income from continuing operations	59,540	44,712	110,472	83,731
Operating (loss) income from discontinued operations	(373)	(145)	(755)	(648)
Tax (benefit) on (loss) income from discontinued operations	(136)	4	(275)	168
Income (loss) from discontinued operations	(237)	(149)	(480)	(816)
Net income	59,303	44,563	109,992	82,915
Less: Income from continuing operations attributable to noncontrolling interest	0	0	0	0
Net income attributable to common shareholders	59,303	44,563	109,992	82,915
Other comprehensive loss attributable to common shareholders	(8,441)	20,986	14,753	(60,215)
Comprehensive income attributable to common shareholders	50,862	65,549	124,745	22,700
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Net revenues	280,430	269,703	539,341	533,864
Cost of goods sold	170,700	158,718	326,241	317,044
Gross profit	109,730	110,985	213,100	216,820
Selling, general and administrative expenses	86,385	82,844	167,862	167,112
Research and development expenses	8,644	4,894	15,079	16,021
Restructuring charges	557	591	5,315	4,330
Gain on sale of assets	(378)		(378)
Income from continuing operations before interest and taxes	14,522	22,656	25,222	29,357
Interest, net	(22,437)	(18,565)	(42,755)	(37,134)
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	36,959	41,221	67,977	66,491
(Benefit) taxes on (loss) income from continuing operations	14,504	14,917	26,181	25,909
Equity in net income of consolidated subsidiaries	63,605	51,964	121,505	111,654
Income from continuing operations	86,060	78,268	163,301	152,236
Operating (loss) income from discontinued operations	0	0	0	0
Tax (benefit) on (loss) income from discontinued operations	0	0	0	0
Income (loss) from discontinued operations	0	0	0	0
Net income	86,060	78,268	163,301	152,236
Less: Income from continuing operations attributable to noncontrolling interest	0	0	0	0
Net income attributable to common shareholders	86,060	78,268	163,301	152,236
Other comprehensive loss attributable to common shareholders	(9,685)	45,015	8,888	(61,746)
Comprehensive income attributable to common shareholders	76,375	123,283	172,189	90,490
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Net revenues	290,784	276,258	552,132	535,159
Cost of goods sold	146,997	152,355	279,960	289,973
Gross profit	143,787	123,903	272,172	245,186
Selling, general and administrative expenses	46,297	50,964	91,356	94,781
Research and development expenses	6,688	8,549	12,606	10,306
Restructuring charges	(676)	(11)	4,534	698
Gain on sale of assets	0		(1,019)
Income from continuing operations before interest and taxes	91,478	64,401	164,695	139,401
Interest, net	1,069	1,260	2,047	2,472
Loss on extinguishment of debt	0	0	0	0
Income from continuing operations before taxes	90,409	63,141	162,648	136,929
(Benefit) taxes on (loss) income from continuing operations	15,909	8,463	23,773	23,207
Equity in net income of consolidated subsidiaries	175	122	343	219
Income from continuing operations	74,675	54,800	139,218	113,941
Operating (loss) income from discontinued operations	379	0	379	4
Tax (benefit) on (loss) income from discontinued operations	(51)	41	18	81
Income (loss) from discontinued operations	430	(41)	361	(77)
Net income	75,105	54,759	139,579	113,864
Less: Income from continuing operations attributable to noncontrolling interest	285	446	464	664
Net income attributable to common shareholders	74,820	54,313	139,115	113,200
Other comprehensive loss attributable to common shareholders	(11,378)	24,340	11,034	(75,388)
Comprehensive income attributable to common shareholders	$ 63,442	$ 78,653	$ 150,149	$ 37,812