Pension and Other Postretirement Benefits - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service (cost) credit	$ (0.9)	$ (1.1)
Net actuarial (loss) gain	(367.3)	(370.6)
Accumulated other comprehensive income (loss) – pretax	(368.2)	(371.7)
Accumulated other comprehensive income (loss) – net of tax	(277.2)	(226.1)
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service (cost) credit	0.0	(0.1)
Net actuarial (loss) gain	5.5	4.2
Accumulated other comprehensive income (loss) – pretax	5.5	4.1
Accumulated other comprehensive income (loss) – net of tax	$ 3.7	$ 2.6

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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-Publisher FASB
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Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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-Publisher FASB
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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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