Basis of presentation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2020	Mar. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Intangible asset amortization expense	$ 38,911	$ 37,751
Cost of Goods Sold | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Intangible asset amortization expense	20,900	20,800
Selling, General and Administrative Expenses | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Intangible asset amortization expense	$ (20,900)	$ (20,800)