Pension, Post-Retirement and Post-Employment Plans - Fair Value of Plan Assets by Asset Category (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	$ 167.9	$ 159.7
Assets using net asset value (or NAV) as a practical expedient	44.7	101.9
Total	212.6	261.6
Domestic equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	31.8	31.1
Foreign equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	18.3	0.0
Mutual funds holding domestic securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	4.0	5.5
U.S. Treasuries | Level 2
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	14.6	4.9
Mutual funds holding U.S. Treasury Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	9.2	12.0
Mutual funds holding fixed income securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	74.6	14.6
Insurance Buy-In Policy | Level 3
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	0.0	70.2
Foreign public bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	5.3	5.1
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	0.0	1.2
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Sub-Total	$ 10.1	$ 15.1