Restructuring and other impairment charges - expected costs to be incurred (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
2019 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges	$ 13.8
Restructuring expenses	6.1
Aggregate restructuring related charges	6.6
2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	56.0
Expected cash outlays	53.0
Expected capital expenditures	29.0
2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	70.0
Expected cash outlays	66.0
Expected capital expenditures	35.0
2018 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges	54.1
Restructuring expenses	3.0
Aggregate restructuring related charges	7.2
2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	102.0
Expected cash outlays	99.0
Expected capital expenditures	19.0
2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	133.0
Expected cash outlays	127.0
Expected capital expenditures	23.0
2014 Footprint realignment plan
Restructuring Cost and Reserve [Line Items]
Aggregate restructuring charges	13.0
Restructuring expenses	3.2
Aggregate restructuring related charges	32.2
2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	47.0
Expected cash outlays	38.0
Expected capital expenditures	25.0
2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	52.0
Expected cash outlays	43.0
Expected capital expenditures	30.0
Termination benefits | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	19.0
Termination benefits | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	23.0
Termination benefits | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	60.0
Termination benefits | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	70.0
Termination benefits | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	12.0
Termination benefits | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	13.0
Other costs | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	1.0
Other costs | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0
Other costs | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0
Other costs | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	4.0
Other costs | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	1.0
Other costs | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	2.0
Special Termination Benefit And Other Restructuring | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	20.0
Special Termination Benefit And Other Restructuring | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	25.0
Special Termination Benefit And Other Restructuring | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	62.0
Special Termination Benefit And Other Restructuring | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	74.0
Special Termination Benefit And Other Restructuring | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	13.0
Special Termination Benefit And Other Restructuring | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	15.0
Accelerated Depreciation And Other Costs | 2019 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	36.0
Accelerated Depreciation And Other Costs | 2019 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	45.0
Accelerated Depreciation And Other Costs | 2018 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	40.0
Accelerated Depreciation And Other Costs | 2018 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	59.0
Accelerated Depreciation And Other Costs | 2014 Footprint realignment plan | Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	34.0
Accelerated Depreciation And Other Costs | 2014 Footprint realignment plan | Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges	$ 37.0