Future minimum lease payments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Rent Expense	$ 366.1	$ 358.5	$ 369.5
Rent Obligations, due 2013	327.6
Rent Obligations, due 2014	296.9
Rent Obligations, due 2015	247.9
Rent Obligations, due 2016	201.9
Rent Obligations, due 2017	180.2
Rent Obligations, due thereafter	702.7
Total Rent Obligations	1,957.2
Sublease Rental Income, due 2013	(17.0)
Sublease Rental Income, due 2014	(8.5)
Sublease Rental Income, due 2015	(2.6)
Sublease Rental Income, due 2016	(0.6)
Sublease Rental Income, due 2017	0
Sublease Rental Income, due thereafter	0
Total Sublease Rental Income	(28.7)
Net Rent, due 2013	310.6
Net Rent, due 2014	288.4
Net Rent, due 2015	245.3
Net Rent, due 2016	201.3
Net Rent, due 2017	180.2
Net Rent, due thereafter	702.7
Total Net Rent	1,928.5
Operating Leases, Rent Expense, Sublease Rentals	16.1	17.5	19.4
Operating Leases, Rent Expense, Net	$ 350.0	$ 341.0	$ 350.1

Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Current

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Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Due in Five Years

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Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Due in Four Years

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Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Due in Two Years

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Operating Leases, Future Minimum Payments, Gross Rent, Due in Three Years

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

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Amount of required minimum rental payments maturing in the next fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Contractually required future rental payments receivable on noncancelable subleasing arrangements.

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Amount of required minimum rental payments maturing in the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Amount of required minimum rental payments maturing in the forth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Amount of required minimum rental payments maturing in the third fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Amount of required minimum rental payments maturing in the second fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Amount of required minimum rental payments maturing after the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases.

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