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Retirement Benefits (Details1) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Pension Plans Defined Benefit    
Defined Benefit Plan Disclosure [Line Items]    
Service cost - benefits earned during the year $ 3.5 $ 5.2
Interest cost on benefits earned in prior years 29.2 31.4
Expected return on plan assets (36.7) (37.2)
Amortization of prior service cost (credit) 0.3 0.3
Amortization of net actuarial loss 15.6 16.3
Total retirement benefit expense 11.9 16.0
Other Postretirement Benefit Plan, Defined Benefit    
Defined Benefit Plan Disclosure [Line Items]    
Service cost - benefits earned during the year 0.6 0.6
Interest cost on benefits earned in prior years 3.7 4.1
Expected return on plan assets 0.0 0.0
Amortization of prior service cost (credit) (0.7) 0.6
Amortization of net actuarial loss 2.2 2.4
Total retirement benefit expense $ 5.8 $ 7.7