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Pension and Other Postretirement Benefits - Pension Plan Asset Allocation (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	100.00%	100.00%
Fair value of assets	$ 261.7	$ 303.3
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	261.7	303.3
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0.0	0.0
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0.0	$ 0.0
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	26.00%
Actual plan asset allocations	25.00%	29.00%
Fair value of assets	$ 66.5	$ 86.5
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	66.5	86.5
U.S. Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0.0	0.0
U.S. Equities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0.0	$ 0.0
International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	22.00%
Actual plan asset allocations	19.00%	26.00%
Fair value of assets	$ 49.0	$ 79.1
International Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	49.0	79.1
International Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0.0	0.0
International Equities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0.0	$ 0.0
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	52.00%
Actual plan asset allocations	56.00%	45.00%
Fair value of assets	$ 146.2	$ 137.7
Fixed Income Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	146.2	137.7
Fixed Income Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0.0	0.0
Fixed Income Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0.0	$ 0.0

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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