Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Rent Expense [Abstract]
Rent expense, Net	$ 411.5	$ 404.5	$ 442.7
Future Minimum Lease Payments Under Non-Cancelable Operating Leases [Abstract]
Operating leases, future minimum lease payments, Gross rent, 2012	364.9
Operating leases, future minimum lease payments, Gross rent, 2013	298.4
Operating leases, future minimum lease payments, Gross rent, 2014	228.3
Operating leases, future minimum lease payments, Gross rent, 2015	176.4
Operating leases, future minimum lease payments, Gross rent, 2016	129.7
Operating leases, future minimum lease payments, Gross rent, Thereafter	385.4
Operating leases, future minimum lease payments, Gross rent	1,583.1
Operating leases, future minimum lease payments, Sublease rent, 2012	6.9
Operating leases, future minimum lease payments, Sublease rent, 2013	4.8
Operating leases, future minimum lease payments, Sublease rent, 2014	4.0
Operating leases, future minimum lease payments, Sublease rent, 2015	3.2
Operating leases, future minimum lease payments, Sublease rent, 2016	1.0
Operating leases, future minimum lease payments, Sublease rent, Thereafter	1.2
Operating leases, future minimum lease payments, Sublease rent	21.1
Operating leases, future minimum lease payments, Net rent, 2012	358.0
Operating leases, future minimum lease payments, Net rent, 2013	293.6
Operating leases, future minimum lease payments, Net rent, 2014	224.3
Operating leases, future minimum lease payments, Net rent, 2015	173.2
Operating leases, future minimum lease payments, Net rent, 2016	128.7
Operating leases, future minimum lease payments, Net rent, Thereafter	384.2
Operating leases, future minimum lease payments, Net rent	1,562.0
Future Minimum Lease Payments Under Non-Cancelable Capital Leases [Abstract]
Capital leases, future minimum lease payments, 2012	24.9
Capital leases, future minimum lease payments, 2013	16.3
Capital leases, future minimum lease payments, 2014	8.5
Capital leases, future minimum lease payments, 2015	3.7
Capital leases, future minimum lease payments, 2016	2.2
Capital leases, future minimum lease payments, Thereafter	2.2
Capital leases, future minimum lease payments, Total	57.8
Capital leases, future minimum lease payments, interest component	1.9
Capital leases, future minimum lease payments, present value	55.9
Capital lease obligations, current portion	24.1	20.3
Capital lease obligations, long-term portion	31.8	30.7
Property under capital leases	111.4	94.6
Property under capital leases, accumulated amortization	59.4	46.0
Property under capital leases, amortization expense	25.0	23.0	17.0
Office [Member]
Rent Expense [Abstract]
Rent expense, Office rent	381.6	374.4	396.0
Rent expense, Third party sublease rent	12.8	16.3	18.9
Rent expense, Net	368.8	358.1	377.1
Equipment [Member]
Rent Expense [Abstract]
Rent expense, Net	$ 42.7	$ 46.4	$ 65.6