Retirement Benefits (Details 6) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 2.1	$ 0.0
Current liabilities	(5.3)	(5.2)
Noncurrent liabilities	(697.0)	(827.9)
Total amount recognized	(700.2)	(833.1)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0.0	0.0
Current liabilities	(31.5)	(36.4)
Noncurrent liabilities	(317.8)	(317.7)
Total amount recognized	$ (349.3)	$ (354.1)