Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 24.3	$ 5.9	$ 30.2	$ 11.0
Other comprehensive income:
Amortization of actuarial losses and prior service credits, net of income taxes	9.4	9.0	19.1	18.1
Comprehensive income	$ 33.7	$ 14.9	$ 49.3	$ 29.1

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
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e557-108580

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
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-Paragraph 1
-Subparagraph (SX 210.9-04(22))
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-Topic 225
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-Paragraph 2
-Subparagraph (SX 210.5-03(20))
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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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