Leases Maturities of lease liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2019		Jan. 01, 2019	Dec. 31, 2018
Maturities of lease liabilities [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year		$ 361.7
Lessee, Operating Lease, Liability, Payments, Due Year Two		271.1
Lessee, Operating Lease, Liability, Payments, Due Year Three		144.7
Lessee, Operating Lease, Liability, Payments, Due Year Four		106.7
Lessee, Operating Lease, Liability, Payments, Due Year Five		85.3
Lessee, Operating Lease, Liability, Payments, Due after Year Five		412.5
Lessee, Operating Lease, Liability, Payments, Due		1,382.0
Lessee, Operating Lease, Imputed interest	[1]	248.1
Operating lease liability		$ 1,133.9	[2]	$ 1,189.6
Operating Leases, Future Minimum Payments Due, Next Twelve Months					$ 329.8
Operating Leases, Future Minimum Payments, Due in Two Years					286.1
Operating Leases, Future Minimum Payments, Due in Three Years					192.3
Operating Leases, Future Minimum Payments, Due in Four Years					123.8
Operating Leases, Future Minimum Payments, Due in Five Years					102.1
Operating Leases, Future Minimum Payments, Due Thereafter					485.6
Operating Leases, Future Minimum Payments Due					1,519.7
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals					25.6
Operating Leases, Future Minimum Payments Due, Net of Future Sublease Rental Income					$ 1,494.1

[1] Calculated using the interest rate for each lease.

[2] Includes the current portion of $308.7 million for operating leases.