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Derivative financial instruments - Narratives (Details)	3 Months Ended
Derivative financial instruments - Narratives (Details)	Mar. 28, 2020 USD ($) instrument	Mar. 30, 2019 USD ($)	Mar. 28, 2020 EUR (€) instrument	Dec. 28, 2019 USD ($) instrument
Interest rate swaps due June 30, 2020 through June 30, 2023
Derivative
Notional amount of derivative contracts	$ 870,000,000.0			$ 870,000,000.0
Number of derivative instruments (instruments) \| instrument	3		3	3
Interest rate cap
Derivative
Notional amount of derivative contracts	$ 1,700,000,000			$ 1,700,000,000
Not designated as hedging instrument
Derivative
Gain (loss) on derivative, recognized in the income statement	800,000	$ 2,900,000
Not designated as hedging instrument \| —Currency swaps
Derivative
Notional amount of derivative contracts	270,000,000.0			270,000,000.0
Not designated as hedging instrument \| Currency forward contracts
Derivative
Notional amount of derivative contracts	32,300,000			16,700,000
Not designated as hedging instrument \| Forward contracts
Derivative
Notional amount of derivative contracts	64,300,000			$ 82,500,000
Derivatives designated as hedging instruments: \| Euro Term Loan \| Secured debt \| Net investment hedges
Derivative
Debt instrument principal amount \| €			€ 147,000,000.0
Derivatives designated as hedging instruments: \| —Currency swaps \| Net investment hedges \| Interest expense
Derivative
Gain (loss) on derivative, recognized in the income statement	$ (1,600,000)	$ 2,200,000