Accounting Policies (Property and Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Land	$ 248.9	$ 254.4
Structures	769.5	789.3
Revenue equipment	1,375.2	1,430.1
Technology equipment and software	186.8	146.4
Other	206.6	202.6
Total cost	2,787.0	2,822.8
Depreciation	$ 146.3	$ 145.5	$ 145.1
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