Restructuring and impairment charges (credits) - expected costs to be incurred (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 28, 2020 USD ($)	Jun. 28, 2020 USD ($)
2019 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges		$ 15.0
Restructuring reserve	$ 12.4	12.4
Restructuring expenses	3.9	6.4
Aggregate restructuring related charges		13.0
2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	58.0	58.0
Expected cash outlays	55.0	55.0
Expected capital expenditures	27.0	27.0
2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	67.0	67.0
Expected cash outlays	63.0	63.0
Expected capital expenditures	33.0	33.0
2018 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges		62.1
Restructuring reserve	50.5	50.5
Restructuring expenses	1.5	2.7
Aggregate restructuring related charges		9.9
2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	102.0	102.0
Expected cash outlays	99.0	99.0
Expected capital expenditures	19.0	19.0
2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	133.0	133.0
Expected cash outlays	127.0	127.0
Expected capital expenditures	23.0	23.0
2014 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges		13.4
Restructuring reserve	3.7	3.7
Restructuring expenses	0.8	1.7
Aggregate restructuring related charges		33.9
Increase (decrease) in restructuring reserve		3.0
2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	51.0	51.0
Expected cash outlays	42.0	42.0
Expected capital expenditures	25.0	25.0
2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	55.0	55.0
Expected cash outlays	46.0	46.0
Expected capital expenditures	26.0	26.0
Termination benefits | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	10.0	10.0
Termination benefits | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	13.0	13.0
Termination benefits | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	16.0	16.0
Termination benefits | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	20.0	20.0
Termination benefits | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	60.0	60.0
Termination benefits | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	70.0	70.0
Termination benefits | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	12.0	12.0
Termination benefits | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	13.0	13.0
Other Restructuring costs | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0	2.0
Other Restructuring costs | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0	2.0
Other Restructuring costs | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0	2.0
Other Restructuring costs | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	4.0	4.0
Other Restructuring costs | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	1.0	1.0
Other Restructuring costs | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0	2.0
Special Termination Benefit And Other Restructuring | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	18.0	18.0
Special Termination Benefit And Other Restructuring | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	22.0	22.0
Special Termination Benefit And Other Restructuring | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	62.0	62.0
Special Termination Benefit And Other Restructuring | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	74.0	74.0
Special Termination Benefit And Other Restructuring | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	13.0	13.0
Special Termination Benefit And Other Restructuring | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	15.0	15.0
Accelerated Depreciation And Other Costs | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	40.0	40.0
Accelerated Depreciation And Other Costs | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	45.0	45.0
Accelerated Depreciation And Other Costs | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	40.0	40.0
Accelerated Depreciation And Other Costs | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	59.0	59.0
Accelerated Depreciation And Other Costs | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	38.0	38.0
Accelerated Depreciation And Other Costs | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	$ 40.0	$ 40.0