Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Liabilities	$ 204.0	$ 107.8
Deferred expenditures	78.9	73.6
Employee benefits	82.4	45.5
Tax losses / credits	152.7	199.2
Intangible assets	17.7	18.5
Other	3.7	10.8
Total deferred tax assets, gross	539.4	455.4
Less: valuation allowance	183.5	206.6
Total deferred tax assets	355.9	248.8
Deferred tax liabilities
Property, plant and equipment	(14.7)	(25.2)
Intangible assets	(253.5)	(259.7)
Income recognition	(14.4)	(16.3)
Right-of-use asset	96.7	0.0
Total deferred tax liabilities	(379.3)	(301.2)
Total net deferred tax liabilities	$ (23.4)	$ (52.4)