Employee Retirement Plans (Reconciliation of Projected Benefit Obligation, Fair Value of Plan Assets, and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Changes in benefit obligation
Projected benefit obligation, beginning of year	$ (349.3)	$ (462.7)
Interest cost	(17.6)	(9.7)
Actuarial gain (loss)	(12.4)	86.1
Benefits paid	36.6	37.0
Projected benefit obligation, end of year	(342.7)	(349.3)
Changes in plan assets
Fair value of plan assets, beginning of year	313.0	443.5
Actual gain (loss) on plan assets	26.2	(94.5)
Employer contributions	0.7	1.0
Benefits paid	(36.6)	(37.0)
Fair value of plan assets, end of year	303.3	313.0
Underfunded status	$ (39.4)	$ (36.3)