Retirement Benefits (Details 8) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	$ (2.3)	$ (3.6)
Net actuarial loss	(1,460.4)	(1,414.6)
Accumulated other comprehensive loss	(1,462.7)	(1,418.2)	$ (1,352.1)
Deferred tax effect	543.4	529.9
Accumulated other comprehensive loss, net of tax	(919.3)	(888.3)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	14.6	(6.9)
Net actuarial loss	(89.0)	(94.5)
Accumulated other comprehensive loss	(74.4)	(101.4)	$ (152.9)
Deferred tax effect	28.2	38.5
Accumulated other comprehensive loss, net of tax	$ (46.2)	$ (62.9)