Income Taxes - Deferred Income Tax Assets And Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Inventories	$ 17.5	$ 17.9
Pension benefits	13.3	19.2
Other accruals and prepayments	51.0	41.5
Lease liabilities	45.4	51.1
Stock-based compensation expense	6.0	3.0
Unrealized gains and losses	30.9	4.5
Tax credit and loss carryforwards	159.5	152.0
Valuation allowances	(126.0)	(119.1)
Total deferred tax asset	197.6	170.1
Deferred tax liabilities:
Property, plant and equipment	(14.5)	(8.3)
Interest expense	(2.3)	0.0
Right-of-use assets	(40.6)	(48.2)
Goodwill and other intangible assets	(278.0)	(339.0)
Total deferred tax liability	(335.4)	(395.5)
Net deferred tax liability	$ (137.8)	$ (225.4)