Pension and Postretirement Health and Life Benefits (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Plan, Defined Benefit [Member]
Service costs	$ 0.8	$ 0.9	$ 2.4	$ 2.5
Interest costs	7.5	7.1	22.7	21.5
Expected return on plan assets (gains)	(9.1)	(10.3)	(27.3)	(30.7)
Net periodic benefit cost (credit)	(0.8)	(2.3)	(2.2)	(6.7)
Postretirement Health and Life Benefits Plans [Member]
Interest costs	1.5	1.5	4.5	4.4
Amortization of prior service costs (credits), net	0.0	0.0	(0.1)	(0.1)
Net periodic benefit cost (credit)	$ 1.5	$ 1.5	$ 4.4	$ 4.3