Condensed consolidating guarantor financial information - Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 25, 2016	Dec. 31, 2015	Sep. 27, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 499,459	$ 338,366	$ 276,463	$ 303,236
Accounts receivable, net	261,833	262,416
Accounts receivable from consolidated subsidiaries	0	0
Inventories, net	341,830	330,275
Prepaid expenses and other current assets	34,354	34,915
Prepaid taxes	22,259	30,895
Assets held for sale	4,137	6,972
Total current assets	1,163,872	1,003,839
Property, plant and equipment, net	322,019	316,123
Goodwill	1,305,078	1,295,852
Intangible assets, net	1,164,644	1,199,975
Investments in affiliates	27	152
Deferred tax assets	2,792	2,341
Notes receivable and other amounts due from consolidated subsidiaries	0	0
Other assets	43,237	53,492
Total assets	4,001,669	3,871,774
Current liabilities
Current borrowings	181,895	417,350
Accounts payable	70,246	66,305
Accounts payable to consolidated subsidiaries	0	0
Accrued expenses	68,972	64,017
Current portion of contingent consideration	7,539	7,291
Payroll and benefit-related liabilities	81,746	84,658
Accrued interest	12,611	7,480
Income taxes payable	11,271	8,059
Other current liabilities	18,122	8,960
Total current liabilities	452,402	664,120
Long-term borrowings	849,967	641,850
Deferred tax liabilities	311,390	315,983
Pension and postretirement benefit liabilities	131,222	149,441
Noncurrent liability for uncertain tax positions	26,693	40,400
Notes payable and other amounts due to consolidated subsidiaries	0	0
Other liabilities	60,073	48,887
Total liabilities	1,831,747	1,860,681
Total common shareholders' equity	2,169,922	2,009,272
Noncontrolling interest	0	1,821
Total equity	2,169,922	2,011,093
Total liabilities and equity	4,001,669	3,871,774
Reportable Legal Entities | Parent Company
Current assets
Cash and cash equivalents	33,460	21,612	37,898	27,996
Accounts receivable, net	2,478	2,538
Accounts receivable from consolidated subsidiaries	4,610	5,276
Inventories, net	0	0
Prepaid expenses and other current assets	8,929	10,511
Prepaid taxes	5,154	16,686
Assets held for sale	0	2,901
Total current assets	54,631	59,524
Property, plant and equipment, net	2,654	2,931
Goodwill	0	0
Intangible assets, net	0	0
Investments in affiliates	6,005,108	5,724,226
Deferred tax assets	90,853	91,432
Notes receivable and other amounts due from consolidated subsidiaries	1,362,709	1,358,446
Other assets	22,446	22,602
Total assets	7,538,401	7,259,161
Current liabilities
Current borrowings	131,895	374,050
Accounts payable	3,960	1,945
Accounts payable to consolidated subsidiaries	2,232,673	2,478,109
Accrued expenses	15,920	15,399
Current portion of contingent consideration	0	0
Payroll and benefit-related liabilities	18,562	21,617
Accrued interest	12,592	7,455
Income taxes payable	0	0
Other current liabilities	2,413	1,300
Total current liabilities	2,418,015	2,899,875
Long-term borrowings	849,967	641,850
Deferred tax liabilities	0	0
Pension and postretirement benefit liabilities	83,905	100,355
Noncurrent liability for uncertain tax positions	1,749	1,151
Notes payable and other amounts due to consolidated subsidiaries	1,991,921	1,585,727
Other liabilities	22,922	20,931
Total liabilities	5,368,479	5,249,889
Total common shareholders' equity	2,169,922	2,009,272
Noncontrolling interest		0
Total equity		2,009,272
Total liabilities and equity	7,538,401	7,259,161
Reportable Legal Entities | Guarantor Subsidiaries
Current assets
Cash and cash equivalents	1,024	0	40	0
Accounts receivable, net	6,249	4,326
Accounts receivable from consolidated subsidiaries	2,167,693	2,412,079
Inventories, net	209,912	205,163
Prepaid expenses and other current assets	5,976	4,702
Prepaid taxes	0	0
Assets held for sale	0	0
Total current assets	2,390,854	2,626,270
Property, plant and equipment, net	163,396	174,674
Goodwill	708,805	705,753
Intangible assets, net	691,398	762,084
Investments in affiliates	1,544,772	1,360,045
Deferred tax assets	0	0
Notes receivable and other amounts due from consolidated subsidiaries	2,067,932	1,658,092
Other assets	6,704	6,615
Total assets	7,573,861	7,293,533
Current liabilities
Current borrowings	0	0
Accounts payable	32,551	27,527
Accounts payable to consolidated subsidiaries	236,780	201,400
Accrued expenses	17,603	22,281
Current portion of contingent consideration	7,539	7,291
Payroll and benefit-related liabilities	23,679	29,305
Accrued interest	0	0
Income taxes payable	0	0
Other current liabilities	3,042	2,679
Total current liabilities	321,194	290,483
Long-term borrowings	0	0
Deferred tax liabilities	370,943	376,738
Pension and postretirement benefit liabilities	31,376	32,274
Noncurrent liability for uncertain tax positions	17,899	17,722
Notes payable and other amounts due to consolidated subsidiaries	1,237,297	1,253,189
Other liabilities	24,812	15,685
Total liabilities	2,003,521	1,986,091
Total common shareholders' equity	5,570,340	5,307,442
Noncontrolling interest		0
Total equity		5,307,442
Total liabilities and equity	7,573,861	7,293,533
Reportable Legal Entities | Non-Guarantor Subsidiaries
Current assets
Cash and cash equivalents	464,975	316,754	238,525	275,240
Accounts receivable, net	249,190	251,166
Accounts receivable from consolidated subsidiaries	330,802	289,697
Inventories, net	160,241	149,705
Prepaid expenses and other current assets	15,784	16,037
Prepaid taxes	17,105	14,622
Assets held for sale	4,137	4,071
Total current assets	1,242,234	1,042,052
Property, plant and equipment, net	155,969	138,518
Goodwill	596,273	590,099
Intangible assets, net	473,246	437,891
Investments in affiliates	23,335	23,065
Deferred tax assets	6,947	8,042
Notes receivable and other amounts due from consolidated subsidiaries	0	0
Other assets	14,087	24,275
Total assets	2,512,091	2,263,942
Current liabilities
Current borrowings	50,000	43,300
Accounts payable	33,735	36,833
Accounts payable to consolidated subsidiaries	33,652	27,543
Accrued expenses	35,449	26,337
Current portion of contingent consideration	0	0
Payroll and benefit-related liabilities	39,505	33,736
Accrued interest	19	25
Income taxes payable	11,424	8,144
Other current liabilities	12,667	4,981
Total current liabilities	216,451	180,899
Long-term borrowings	0	0
Deferred tax liabilities	35,455	36,378
Pension and postretirement benefit liabilities	15,941	16,812
Noncurrent liability for uncertain tax positions	7,045	21,527
Notes payable and other amounts due to consolidated subsidiaries	201,423	177,622
Other liabilities	12,339	12,271
Total liabilities	488,654	445,509
Total common shareholders' equity	2,023,437	1,816,612
Noncontrolling interest		1,821
Total equity		1,818,433
Total liabilities and equity	2,512,091	2,263,942
Consolidation, Eliminations
Current assets
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable, net	3,916	4,386
Accounts receivable from consolidated subsidiaries	(2,503,105)	(2,707,052)
Inventories, net	(28,323)	(24,593)
Prepaid expenses and other current assets	3,665	3,665
Prepaid taxes	0	(413)
Assets held for sale	0	0
Total current assets	(2,523,847)	(2,724,007)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Investments in affiliates	(7,573,188)	(7,107,184)
Deferred tax assets	(95,008)	(97,133)
Notes receivable and other amounts due from consolidated subsidiaries	(3,430,641)	(3,016,538)
Other assets	0	0
Total assets	(13,622,684)	(12,944,862)
Current liabilities
Current borrowings	0	0
Accounts payable	0	0
Accounts payable to consolidated subsidiaries	(2,503,105)	(2,707,052)
Accrued expenses	0	0
Current portion of contingent consideration	0	0
Payroll and benefit-related liabilities	0	0
Accrued interest	0	0
Income taxes payable	(153)	(85)
Other current liabilities	0	0
Total current liabilities	(2,503,258)	(2,707,137)
Long-term borrowings	0	0
Deferred tax liabilities	(95,008)	(97,133)
Pension and postretirement benefit liabilities	0	0
Noncurrent liability for uncertain tax positions	0	0
Notes payable and other amounts due to consolidated subsidiaries	(3,430,641)	(3,016,538)
Other liabilities	0	0
Total liabilities	(6,028,907)	(5,820,808)
Total common shareholders' equity	(7,593,777)	(7,124,054)
Noncontrolling interest		0
Total equity		(7,124,054)
Total liabilities and equity	$ (13,622,684)	$ (12,944,862)