Fair value measurement - Schedule of carrying amount and fair value of debt (Details) - USD ($) $ in Millions	Jun. 27, 2020	Dec. 28, 2019
Carrying amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Current	$ 63.5	$ 46.1
Non-current	2,906.9	2,912.3
Fair value of debt	2,970.4	2,958.4
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Current	62.4	45.9
Non-current	2,859.8	2,946.8
Fair value of debt	$ 2,922.2	$ 2,992.7

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
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Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

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