Accounting Policies (Estimated Cash Payments) (Details) $ in Millions	Dec. 31, 2016 USD ($)
Workers' Compensation [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
2017	$ 76.2
2018	50.5
2019	34.9
2020	23.9
2021	18.3
Thereafter	95.6
Total	299.4
Property Damage and Liability Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
2017	29.3
2018	19.3
2019	12.4
2020	6.7
2021	3.1
Thereafter	2.1
Total	72.9
Total [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
2017	105.5
2018	69.8
2019	47.3
2020	30.6
2021	21.4
Thereafter	97.7
Total	$ 372.3