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Derivative financial instruments - Narratives (Details)	3 Months Ended		6 Months Ended
Derivative financial instruments - Narratives (Details)	Jun. 27, 2020 USD ($) instrument	Jun. 29, 2019 USD ($)	Jun. 27, 2020 USD ($) instrument	Jun. 29, 2019 USD ($)	Jun. 27, 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			$ 870,000,000.0
Number of derivative instruments (instruments) \| instrument	3		3		3	3
Interest rate cap
Derivative
Notional amount of derivative contracts	$ 1,700,000,000		$ 1,700,000,000			$ 1,700,000,000
Not designated as hedging instrument
Derivative
Gain (loss) on derivative, recognized in the income statement	(400,000)	$ (1,200,000)	400,000	$ 1,700,000
Not designated as hedging instrument \| —Currency swaps
Derivative
Notional amount of derivative contracts	270,000,000.0		270,000,000.0			270,000,000.0
Not designated as hedging instrument \| Currency forward contracts
Derivative
Notional amount of derivative contracts	12,400,000		12,400,000			16,700,000
Not designated as hedging instrument \| Forward contracts
Derivative
Notional amount of derivative contracts	85,700,000		85,700,000			$ 82,500,000
Derivatives designated as hedging instruments:
Derivative
Loss reclassfication from accumulated in OCI			53,700,000
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	$ 1,300,000	$ 2,000,000.0	$ 2,900,000	$ 4,200,000