Pension Plans and Other Postretirement Benefit Plans - Pension Plans and Other Postretirement Benefit (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Funded status of fully funded, underfunded, and unfunded pension plans:
Overfunded defined benefit pension plans	$ 5.9	$ 5.7
Unfunded defined benefit pension plans	430.5	433.1
Pension liabilities included in other current liabilities	14.6	14.7
Net funded status	(439.2)	(442.1)
Underfunded Plan
Funded status of fully funded, underfunded, and unfunded pension plans:
Unfunded defined benefit pension plans	67.6	67.1
Unfunded Plan [Member]
Funded status of fully funded, underfunded, and unfunded pension plans:
Unfunded defined benefit pension plans	$ 362.9	$ 366.0

Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as current. Excludes other postretirement benefit plan.

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Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as noncurrent. Excludes other postretirement benefit plan.

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Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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