Operating Leases (Rent Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 155.3	$ 152.8	$ 144.1
Leased Facilities and Equipment [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	109.5	110.1	105.9
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 45.8	$ 42.7	$ 38.2