Principal Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Principal Accounting Policies [Line Items]
Reporting Segments	4
Unearned revenue	$ 16.9	$ 16.6
Deferred setup costs	15.2	15.7
Cash-equivalent investments	378.3	398.5
Variable-rate demand notes	3.2	13.3
Long-term marketable securities		5.4
Depreciation expense	204.9	191.4	178.9
Amortization expense related to capitalized software	8.3	7.9	10.3
Accumulated amortization expense related to capitalized software	155.9	148.4
Book overdrafts	43.0	38.5
Liability related to assumed claims	57.6	57.7
Receivable from the re-insurance pool	39.6	44.0
Operating income from reinsurance pool	$ (2.5)	$ (4.4)	$ 4.1
Buildings [Member]
Principal Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives, years	25
Revenue Equipment [Member]
Principal Accounting Policies [Line Items]
Property, plant and equipment, minimum useful lives, years	4
Property, plant and equipment, maximum useful lives, years	14
Other equipment [Member]
Principal Accounting Policies [Line Items]
Property, plant and equipment, minimum useful lives, years	3
Property, plant and equipment, maximum useful lives, years	10
Software [Member]
Principal Accounting Policies [Line Items]
Property, plant and equipment, minimum useful lives, years	3
Property, plant and equipment, maximum useful lives, years	7