Retirement Benefits (Details 8) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	$ (2.1)	$ (1.0)
Net actuarial loss	(1,468.2)	(1,425.1)
Accumulated other comprehensive loss	(1,470.3)	(1,426.1)	$ (1,462.7)
Deferred tax effect	536.2	525.6
Accumulated other comprehensive loss, net of tax	(934.1)	(900.5)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	8.8	11.7
Net actuarial loss	(115.8)	(95.4)
Accumulated other comprehensive loss	(107.0)	(83.7)	$ (74.4)
Deferred tax effect	35.3	29.7
Accumulated other comprehensive loss, net of tax	$ (71.7)	$ (54.0)