Pension and Postretirement Benefit Plans (Net Pension And Postretirement Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4.0	$ 3.9	$ 12.0	$ 11.7
Interest cost	4.1	5.1	12.3	15.7
Expected return on plan assets	(7.1)	(6.8)	(21.2)	(21.1)
Amortization of net actuarial losses	3.4	2.9	10.0	9.0
Amortization of prior service cost	0.5	0.4	1.6	1.2
Net periodic pension cost	4.9	5.5	14.7	16.5
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.1	0.0	0.1
Interest cost	0.3	0.3	0.9	1.0
Amortization of net actuarial losses	0.1	0.0	0.2	0.0
Amortization of prior service cost	0.0	0.0	0.1	0.1
Net periodic pension cost	$ 0.4	$ 0.4	$ 1.2	$ 1.2