Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 14.0	$ 5.9
Other comprehensive income:
Amortization of actuarial losses and prior service credits, net of $4.2 million and $6.2 million in income taxes in 2018 and 2017, respectively	12.5	9.7
Comprehensive income	26.5	15.6
Income taxes related to defined benefit plan	$ 4.2	$ 6.2

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 5
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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

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