Income Taxes (Income Tax Uncertainties) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Document Period End Date	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 14.4	$ 21.6	$ 29.6
Additions for tax positions of the current year	0.0	0.0	2.3
Additions for tax positions of prior years	7.8	0.5	1.3
Reductions for tax positions of prior years	0.0	(0.8)	(11.3)
Lapses of applicable statutes of limitations	(4.3)	(6.1)	(0.3)
Settlements during the period	(0.1)	(0.8)	0.0
Balance at end of period	17.8	14.4	21.6
Unrecognized tax benefits that would impact the effective tax rate, if recognized	10.5
Interest expense (income)	0.5	(2.8)	(2.5)
Penalties (refunds)	0.0	(0.4)	0.1
Accrued interest related to income tax uncertainties	1.0	0.5
Accrued penalties related to income tax uncertainties	0.1	0.1
Federal rate change	0.0	(0.8)	$ (28.8)
Provisional decrease to deferred income taxes due to Tax Act	(24.5)
Decrease in uncertain tax positions due to Tax Act	0.8
Tax act, provisional income tax benefit	(23.7)
Resolution of Audits or Statute Expirations
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Reasonably possible decrease in unrecognized tax benefits	1.6
Other Current Liabilities
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Accrued interest related to income tax uncertainties	0.5	0.2
Accrued penalties related to income tax uncertainties	0.1	0.1
Other Noncurrent Liabilities
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Accrued interest related to income tax uncertainties	0.5	0.3
Accrued penalties related to income tax uncertainties	$ 0.0	$ 0.0