Income Taxes - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Accruals not yet deductible for tax purposes	$ 16.0	$ 17.4
Net operating loss carryforwards	252.1	245.9
Foreign, federal and state credits	6.5	8.4
Employee benefit items	78.7	79.5
Capitalized expenses	6.2	32.2
Intangibles	24.9	21.8
Derivatives and other	59.8	47.7
Sub-total deferred tax assets	444.2	452.9
Valuation allowance	(207.1)	(197.6)
Total deferred tax assets	237.1	255.3
Depreciation and amortization	(66.0)	(37.0)
Unremitted foreign earnings	(11.0)	(10.0)
Intangible assets	0.0	0.0
Other	(4.0)	(0.4)
Total deferred tax liabilities	(81.0)	(47.4)
Net deferred tax assets	$ 156.1	$ 207.9