Post-retirement benefits - Cumulative losses (gains) not recognized in net period pension plan (Details) - USD ($) $ in Millions	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans
Actuarial (gain) loss	$ (9.5)	$ 21.2	$ 1.5
Prior service costs	11.8	11.1	11.9
Foreign currency translation	(1.2)	(2.9)	(3.9)
Cumulative total	1.1	29.4	9.5
Other post-retirement benefits
Defined Benefit Plans and Other Postretirement Benefit Plans
Actuarial (gain) loss	(16.0)	(17.3)	(16.3)
Prior service costs	(3.0)	(3.4)	(3.8)
Other adjustments	0.2	0.2	0.2
Foreign currency translation	(0.2)	(0.2)	0.0
Cumulative total	$ (19.0)	$ (20.7)	$ (19.9)

Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Actuarial Gain (Loss), before Tax

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- Definition

Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss), before Tax

+ References

No definition available.

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- Definition

Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Other Gain (Loss), before Tax

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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- 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.

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