Accounting Policies (Claims and Insurance) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Workers’ Compensation
LIability For Unpaid Claims And Claim Adjustment Expense, Adjustment Of Opening Balance [Roll Forward]
Undiscounted amount	$ 299.3	$ 299.4
Estimated settlement cost	95.9	95.7
Claim payments, net of recoveries	(92.4)	(90.3)
Change in estimated settlement cost for older claim years	(15.0)	(5.5)
Undiscounted amount	287.8	299.3
Discounted settlement cost estimate			$ 264.4
Undiscounted amount	299.3	299.4	287.8
Property Damage and Liability Claims
LIability For Unpaid Claims And Claim Adjustment Expense, Adjustment Of Opening Balance [Roll Forward]
Undiscounted amount	70.5	72.9
Estimated settlement cost	40.0	37.2
Claim payments, net of recoveries	(36.2)	(33.5)
Change in estimated settlement cost for older claim years	(0.7)	(6.1)
Undiscounted amount	73.6	70.5
Discounted settlement cost estimate			72.0
Undiscounted amount	70.5	72.9	73.6
Total
LIability For Unpaid Claims And Claim Adjustment Expense, Adjustment Of Opening Balance [Roll Forward]
Undiscounted amount	369.8	372.3
Estimated settlement cost	135.9	132.9
Claim payments, net of recoveries	(128.6)	(123.8)
Change in estimated settlement cost for older claim years	(15.7)	(11.6)
Undiscounted amount	361.4	369.8
Discounted settlement cost estimate			336.4
Undiscounted amount	369.8	372.3	361.4
Cargo Claims And Other Insurance Related Amounts [Member]
LIability For Unpaid Claims And Claim Adjustment Expense, Adjustment Of Opening Balance [Roll Forward]
Undiscounted amount	15.0
Undiscounted amount	13.9	15.0
Undiscounted amount	$ 15.0	$ 15.0	$ 13.9