Condensed consolidating guarantor financial information - Balance Sheets (Details) - USD ($) $ in Thousands	Jul. 01, 2018	Dec. 31, 2017	Jul. 02, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 346,304	$ 333,558	$ 676,214	$ 543,789
Accounts receivable, net	359,119	345,875
Accounts receivable from consolidated subsidiaries	0	0
Inventories, net	405,428	395,744
Prepaid expenses and other current assets	52,105	47,882
Prepaid taxes	19,084	5,748
Assets held for sale	3,239	0
Total current assets	1,185,279	1,128,807
Property, plant and equipment, net	410,979	382,999
Goodwill	2,220,888	2,235,592
Intangible assets, net	2,306,204	2,383,748
Investments in consolidated subsidiaries	0	0
Deferred tax assets	2,386	3,810
Notes receivable and other amounts due from consolidated subsidiaries	0	0
Other assets	49,585	46,536
Total assets	6,175,321	6,181,492
Current liabilities
Current borrowings	86,875	86,625
Accounts payable	94,834	92,027
Accounts payable to consolidated subsidiaries	0	0
Accrued expenses	104,340	96,853
Current portion of contingent consideration	110,454	74,224
Payroll and benefit-related liabilities	89,669	107,415
Accrued interest	6,771	6,165
Income taxes payable	5,597	11,514
Other current liabilities	37,905	9,053
Total current liabilities	536,445	483,876
Long-term borrowings	2,145,468	2,162,927
Deferred tax liabilities	596,434	603,676
Pension and postretirement benefit liabilities	113,083	121,410
Noncurrent liability for uncertain tax positions	12,765	12,296
Notes payable and other amounts due to consolidated subsidiaries	0	0
Noncurrent contingent consideration	132,205	197,912
Other liabilities	204,940	168,864
Total liabilities	3,741,340	3,750,961
Total shareholders' equity	2,433,981	2,430,531
Total liabilities and shareholders' equity	6,175,321	6,181,492
Eliminations
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	4,992	4,663
Accounts receivable from consolidated subsidiaries	(1,389,792)	(1,534,839)
Inventories, net	(32,407)	(26,279)
Prepaid expenses and other current assets	3,982	3,982
Prepaid taxes	0	0
Assets held for sale	0
Total current assets	(1,413,225)	(1,552,473)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Investments in consolidated subsidiaries	(7,520,530)	(7,499,941)
Deferred tax assets	(2,284)	(2,261)
Notes receivable and other amounts due from consolidated subsidiaries	(4,568,566)	(4,683,933)
Other assets	0	0
Total assets	(13,504,605)	(13,738,608)
Current liabilities
Current borrowings	0	0
Accounts payable	0	0
Accounts payable to consolidated subsidiaries	(1,389,792)	(1,534,839)
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	(1,103)	0
Other current liabilities	0	0
Total current liabilities	(1,390,895)	(1,534,839)
Long-term borrowings	0	0
Deferred tax liabilities	(2,284)	(2,261)
Pension and postretirement benefit liabilities	0	0
Noncurrent liability for uncertain tax positions	0	0
Notes payable and other amounts due to consolidated subsidiaries	(4,568,566)	(4,683,933)
Noncurrent contingent consideration	0	0
Other liabilities	0	0
Total liabilities	(5,961,745)	(6,221,033)
Total shareholders' equity	(7,542,860)	(7,517,575)
Total liabilities and shareholders' equity	(13,504,605)	(13,738,608)
Parent Company
Current assets
Cash and cash equivalents	50,786	37,803	56,699	14,571
Accounts receivable, net	2,328	2,414
Accounts receivable from consolidated subsidiaries	25,539	14,478
Inventories, net	0	0
Prepaid expenses and other current assets	14,657	14,874
Prepaid taxes	11,811	0
Assets held for sale	0
Total current assets	105,121	69,569
Property, plant and equipment, net	2,887	2,088
Goodwill	0	0
Intangible assets, net	0	0
Investments in consolidated subsidiaries	5,838,568	5,806,244
Deferred tax assets	0	0
Notes receivable and other amounts due from consolidated subsidiaries	2,255,108	2,452,101
Other assets	30,547	31,173
Total assets	8,232,231	8,361,175
Current liabilities
Current borrowings	36,875	36,625
Accounts payable	4,258	4,269
Accounts payable to consolidated subsidiaries	1,033,197	1,211,568
Accrued expenses	18,991	17,957
Current portion of contingent consideration	0	0
Payroll and benefit-related liabilities	15,958	21,145
Accrued interest	6,731	6,133
Income taxes payable	0	4,352
Other current liabilities	874	1,461
Total current liabilities	1,116,884	1,303,510
Long-term borrowings	2,145,468	2,162,927
Deferred tax liabilities	89,938	88,512
Pension and postretirement benefit liabilities	63,481	70,860
Noncurrent liability for uncertain tax positions	1,680	1,117
Notes payable and other amounts due to consolidated subsidiaries	2,240,361	2,155,146
Noncurrent contingent consideration	0	0
Other liabilities	140,438	148,572
Total liabilities	5,798,250	5,930,644
Total shareholders' equity	2,433,981	2,430,531
Total liabilities and shareholders' equity	8,232,231	8,361,175
Guarantor Subsidiaries
Current assets
Cash and cash equivalents	12,626	8,933	10,963	1,031
Accounts receivable, net	49,185	57,818
Accounts receivable from consolidated subsidiaries	1,004,686	1,177,246
Inventories, net	246,255	245,533
Prepaid expenses and other current assets	13,029	9,236
Prepaid taxes	0	0
Assets held for sale	3,239
Total current assets	1,329,020	1,498,766
Property, plant and equipment, net	233,105	213,663
Goodwill	1,245,806	1,246,144
Intangible assets, net	1,312,928	1,355,275
Investments in consolidated subsidiaries	1,661,595	1,674,077
Deferred tax assets	0	0
Notes receivable and other amounts due from consolidated subsidiaries	2,313,458	2,231,832
Other assets	5,880	6,397
Total assets	8,101,792	8,226,154
Current liabilities
Current borrowings	0	0
Accounts payable	53,913	46,992
Accounts payable to consolidated subsidiaries	288,217	261,121
Accrued expenses	33,421	31,827
Current portion of contingent consideration	110,454	74,224
Payroll and benefit-related liabilities	34,341	44,009
Accrued interest	0	0
Income taxes payable	0	0
Other current liabilities	33,609	3,775
Total current liabilities	553,955	461,948
Long-term borrowings	0	0
Deferred tax liabilities	260,624	265,426
Pension and postretirement benefit liabilities	32,283	32,750
Noncurrent liability for uncertain tax positions	8,294	8,196
Notes payable and other amounts due to consolidated subsidiaries	2,125,535	2,320,611
Noncurrent contingent consideration	121,116	186,923
Other liabilities	6,763	7,850
Total liabilities	3,108,570	3,283,704
Total shareholders' equity	4,993,222	4,942,450
Total liabilities and shareholders' equity	8,101,792	8,226,154
Non-Guarantor Subsidiaries
Current assets
Cash and cash equivalents	282,892	286,822	$ 608,552	$ 528,187
Accounts receivable, net	302,614	280,980
Accounts receivable from consolidated subsidiaries	359,567	343,115
Inventories, net	191,580	176,490
Prepaid expenses and other current assets	20,437	19,790
Prepaid taxes	7,273	5,748
Assets held for sale	0
Total current assets	1,164,363	1,112,945
Property, plant and equipment, net	174,987	167,248
Goodwill	975,082	989,448
Intangible assets, net	993,276	1,028,473
Investments in consolidated subsidiaries	20,367	19,620
Deferred tax assets	4,670	6,071
Notes receivable and other amounts due from consolidated subsidiaries	0	0
Other assets	13,158	8,966
Total assets	3,345,903	3,332,771
Current liabilities
Current borrowings	50,000	50,000
Accounts payable	36,663	40,766
Accounts payable to consolidated subsidiaries	68,378	62,150
Accrued expenses	51,928	47,069
Current portion of contingent consideration	0	0
Payroll and benefit-related liabilities	39,370	42,261
Accrued interest	40	32
Income taxes payable	6,700	7,162
Other current liabilities	3,422	3,817
Total current liabilities	256,501	253,257
Long-term borrowings	0	0
Deferred tax liabilities	248,156	251,999
Pension and postretirement benefit liabilities	17,319	17,800
Noncurrent liability for uncertain tax positions	2,791	2,983
Notes payable and other amounts due to consolidated subsidiaries	202,670	208,176
Noncurrent contingent consideration	11,089	10,989
Other liabilities	57,739	12,442
Total liabilities	796,265	757,646
Total shareholders' equity	2,549,638	2,575,125
Total liabilities and shareholders' equity	$ 3,345,903	$ 3,332,771