Income Taxes - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Accruals not yet deductible for tax purposes	$ 17.4	$ 17.5
Net operating loss carryforwards	245.9	265.5
Foreign, federal and state credits	8.4	10.4
Employee benefit items	79.5	77.0
Capitalized expenses	32.2	8.9
Intangibles	21.8	0.0
Derivatives and other	47.7	38.0
Sub-total deferred tax assets	452.9	417.3
Valuation allowance	(197.6)	(218.4)
Total deferred tax assets	255.3	198.9
Depreciation and amortization	(37.0)	(26.8)
Unremitted foreign earnings	(10.0)	0.0
Intangible assets	0.0	(21.7)
Other	(0.4)	(0.4)
Total deferred tax liabilities	(47.4)	(48.9)
Net deferred tax assets	$ 207.9	$ 150.0