Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 542.1	$ 563.1	$ 618.3	$ 612.9	$ 563.1	$ 612.9
Other comprehensive income before reclassifications, before income tax					(1.7)	(0.2)
Amounts reclassified from accumulated other comprehensive income (loss), before income tax					(2.8)	(0.7)
Amounts deferred to accumulated other comprehensive income (loss), before income tax					0.0	67.1
Income tax					0.3	0.0
Other comprehensive income (loss), net of tax	(1.3)	(2.9)	65.7	0.5	(4.2)	66.2
Ending balance	527.0	542.1	673.7	618.3	527.0	673.7
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(6.8)		(7.3)	(6.8)	(7.3)
Other comprehensive income before reclassifications, before income tax					(1.7)	(0.2)
Amounts reclassified from accumulated other comprehensive income (loss), before income tax					0.0	0.0
Amounts deferred to accumulated other comprehensive income (loss), before income tax					0.0	0.0
Income tax					0.0	0.0
Other comprehensive income (loss), net of tax					(1.7)	(0.2)
Ending balance	(8.5)		(7.5)		(8.5)	(7.5)
Pension and Postretirement Liability Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		51.5		(1.6)	51.5	(1.6)
Other comprehensive income before reclassifications, before income tax					0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss), before income tax					(2.8)	(0.7)
Amounts deferred to accumulated other comprehensive income (loss), before income tax					0.0	67.1
Income tax					0.3	0.0
Other comprehensive income (loss), net of tax					(2.5)	66.4
Ending balance	49.0		64.8		49.0	64.8
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	41.8	44.7	(8.4)	(8.9)	44.7	(8.9)
Other comprehensive income (loss), net of tax	(1.3)	(2.9)	65.7	0.5
Ending balance	$ 40.5	$ 41.8	$ 57.3	$ (8.4)	$ 40.5	$ 57.3

Other comprehensive income loss deferrals before tax.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.

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