Retirement Plans - Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Pensions
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss)
Current year net actuarial loss (gain)	$ 1.1	$ 0.9
Current year prior service cost (credit)	0.0	0.1
Total recognized in other comprehensive (income) loss, before taxes	1.1	1.0
Total recognized in other comprehensive (income) loss, after taxes	0.7	0.5
Other Benefits
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss)
Current year net actuarial loss (gain)	0.1	(0.1)
Current year prior service cost (credit)	0.0	0.0
Total recognized in other comprehensive (income) loss, before taxes	0.1	(0.1)
Total recognized in other comprehensive (income) loss, after taxes	$ 0.0	$ 0.1

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- Definition

Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan.

+ References

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-Publisher FASB
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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income from prior service cost (credit) of defined benefit plan.

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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