Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

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Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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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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Ultimate trend rate for health care cost for defined benefit postretirement plan.

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Amount of payment for other postretirement benefits. Excludes pension benefits.

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Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed			6.20%
Ultimate trend rate			4.50%
Effect of one percentage point increase on postretirement benefit obligation			$ 11.6
Effect of one percentage point increase on postretirement benefit cost			$ 0.4
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			39.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			61.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation of pension plans	$ 313.6		$ 270.1
Pension Contributions			0.4
Other postretirement benefits payments	$ 3.5	$ 13.8	$ 18.0	$ 20.5