Employee Retirement Plans (Pension Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension income	$ 4.1	$ 2.7
Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	(2.1)	(3.4)
Expected return on plan assets	6.2	6.1
Net pension income	4.1	$ 2.7
Pension Plans | Non-qualified
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Benefit payments on non-qualified pension plans	0.1
Pension Plans | Qualified
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Contributions on qualified pension plans	$ 0.8