Retirement Benefits (Details 7) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Amortization of net actuarial loss	$ 76.7	$ 89.5	$ 85.3
Amortization to net income (loss) of net prior service credits	(0.5)	(1.8)	(3.1)
Settlement loss (gain) included in net income (loss)	29.5	(21.9)	0.0
Net gain (loss) arising during the period	155.0	155.9	(128.4)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Beginning of year accumulated other comprehensive loss	(1,376.5)	(1,600.3)
Amortization of net actuarial loss	63.5	75.6
Amortization to net income (loss) of net prior service credits	0.4	0.6
Settlement loss (gain) included in net income (loss)	29.5	0.0
Net gain (loss) arising during the period	101.9	147.6
End of year accumulated other comprehensive loss	(1,181.2)	(1,376.5)	(1,600.3)
Net change in accumulated other comprehensive loss	195.3	223.8
Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Beginning of year accumulated other comprehensive loss	(121.2)	(119.1)
Amortization of net actuarial loss	13.2	13.9
Amortization to net income (loss) of net prior service credits	(0.9)	(2.4)
Settlement loss (gain) included in net income (loss)	0.0	(21.9)
Net gain (loss) arising during the period	53.1	8.3
End of year accumulated other comprehensive loss	(55.8)	(121.2)	$ (119.1)
Net change in accumulated other comprehensive loss	$ 65.4	$ (2.1)