Financial instruments - Additional Information (Details) € in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2021 USD ($)	Sep. 27, 2020 USD ($)	Sep. 26, 2021 USD ($)	Sep. 27, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) Financial_Institution_Counterparty	Dec. 31, 2019 EUR (€) Financial_Institution_Counterparty	Dec. 31, 2018 USD ($) Financial_Institution_Counterparty	Dec. 31, 2018 EUR (€) Financial_Institution_Counterparty
Derivatives Fair Value [Line Items]
Allowance for credit losses	$ 11,500,000		$ 11,500,000		$ 12,900,000
Allowance for credit losses, current	6,600,000		6,600,000		8,100,000
Cash flow hedging
Derivatives Fair Value [Line Items]
Ineffectiveness related to derivatives	0	$ 0	0	$ 0
Foreign exchange contract | Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Losses on derivatives	2,700,000	$ 900,000	5,200,000	$ 100,000
Total notional amount for all open foreign currency forward contracts	174,400,000		$ 174,400,000		163,500,000
Derivative, term of contract			12 months
Foreign exchange contract | Designated as Hedging Instrument | Cash flow hedging
Derivatives Fair Value [Line Items]
Total notional amount for all open foreign currency forward contracts	$ 148,400,000		$ 148,400,000		$ 129,500,000
Cross-currency interest rate swaps | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Total notional amount for all open foreign currency forward contracts						$ 250,000,000	€ 219.2	$ 500,000,000	€ 433.9
Derivative, number of instruments held | Financial_Institution_Counterparty						5	5	6	6
Derivative, fixed interest rate						4.875%	4.875%	4.625%	4.625%
Derivative, annual interest rate						2.4595%	2.4595%	1.942%	1.942%