Accounting Policies (Property and Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land	$ 243.7	$ 246.0
Structures	791.3	783.3
Revenue equipment	1,257.4	1,303.5
Technology equipment and software	259.7	230.6
Other	213.8	206.8
Total cost	2,765.9	2,770.2
Depreciation	$ 145.9	$ 147.7	$ 146.3
Structures [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	10 years
Structures [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	30 years
Revenue equipment [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	10 years
Revenue equipment [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	20 years
Technology equipment and software [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	3 years
Technology equipment and software [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	7 years
Other [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	3 years
Other [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, service life	10 years