Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Rent Expense [Abstract]
Rent expense, net	$ 416.4	$ 411.5	$ 404.5
Future Minimum Lease Payments Under Non-Cancelable Operating Leases [Abstract]
Operating Leases, Future Minimum Lease Payments, Gross Rent, 2013	399.7
Operating Leases, Future Minimum Lease Payments, Gross Rent, 2014	298.7
Operating Leases, Future Minimum Lease Payments, Gross Rent, 2015	229.3
Operating Leases, Future Minimum Lease Payments, Gross Rent, 2016	170.0
Operating Leases, Future Minimum Lease Payments, Gross Rent, 2017	146.5
Operating Leases, Future Minimum Lease Payments, Gross Rent, Thereafter	359.4
Operating Leases, Future Minimum Lease Payments, Gross Rent	1,603.6
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, 2013	7.6
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, 2014	6.0
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, 2015	4.0
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, 2016	1.3
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, 2017	1.0
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent, Thereafter	0.2
Operating Leases, Future Minimum Lease Payments, Less Sublease Rent	20.1
Operating Leases, Future Minimum Lease Payments, Net Rent, 2013	392.1
Operating Leases, Future Minimum Lease Payments, Net Rent, 2014	292.7
Operating Leases, Future Minimum Lease Payments, Net Rent, 2015	225.3
Operating Leases, Future Minimum Lease Payments, Net Rent, 2016	168.7
Operating Leases, Future Minimum Lease Payments, Net Rent, 2017	145.5
Operating Leases, Future Minimum Lease Payments, Net Rent, Thereafter	359.2
Operating Leases, Future Minimum Lease Payments, Net Rent	1,583.5
Future Minimum Lease Payments Under Non-Cancelable Capital Leases [Abstract]
Capital Leases, Future Minimum Lease Payments, 2013	24.1
Capital Leases, Future Minimum Lease Payments, 2014	15.6
Capital Leases, Future Minimum Lease Payments, 2015	8.5
Capital Leases, Future Minimum Lease Payments, 2016	4.5
Capital Leases, Future Minimum Lease Payments, 2017	3.2
Capital Leases, Future Minimum Lease Payments, Thereafter	3.1
Capital Leases, Future Minimum Lease Payments, Total minimum lease payments	59.0
Capital Leases, Future Minimum Lease Payments, Less interest component	1.7
Capital Leases, Future Minimum Lease Payments, Present value of minimum lease payments	57.3
Property Under Capital Lease and Capital Lease Obligations [Abstract]
Property under capital lease, Cost	126.3	111.4
Property under capital lease, Accumulated depreciation	(71.3)	(59.4)
Property under capital lease	55.0	52.0
Capital lease obligations, Current	23.4	24.1
Capital lease obligations, Long-term	33.9	31.8
Capital lease obligations	57.3	55.9
Property under capital lease, Depreciation expense	25.9	25.0	23.0
Office [Member]
Rent Expense [Abstract]
Office base rent	390.5	381.6	374.4
Less third party sublease rent	10.4	12.8	16.3
Rent expense, net	380.1	368.8	358.1
Equipment [Member]
Rent Expense [Abstract]
Rent expense, net	$ 36.3	$ 42.7	$ 46.4