Income Taxes - Income Tax Expense Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
U.S. federal statutory rate (percent)	21.00%	21.00%	21.00%
Taxes computed at U.S. statutory rate	$ 17.0	$ 29.6	$ (11.2)
State income taxes, net of federal benefit	2.1	(0.6)	(3.1)
Change in valuation allowances	(4.2)	0.9	27.5
Tax on undistributed foreign earnings	4.3	(3.2)	7.0
Net change in reserve	8.2	(2.1)	(4.9)
Tax rate changes	(1.0)	(0.9)	8.3
Changes to U.S. tax law	(40.4)	0.0	(41.8)
Other, net	2.4	1.8	(0.6)
Income tax expense	$ 4.3	$ 61.3	$ 23.8
Effective tax rate (percent)	5.00%	44.00%	(45.00%)
Domestic
Income Taxes
Tax on foreign operations	$ 8.9	$ 23.7	$ 31.2
Foreign
Income Taxes
Tax on foreign operations	$ 7.0	$ 12.1	$ 11.4

The effective income tax rate reconciliation net change in reserve.

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The effective income tax rate reconciliation provision for tax on undistributed foreign earnings.

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[Line Items] for Income Taxes [Table]

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to Tax Cuts and Jobs Act.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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