Commitments and Contingencies Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Estimated Litigation Liability	$ 0.3	$ 0.3
Future minimum rentals under noncancelable subleases	0.1
Operating leases, rent expense	32.2	30.5	$ 29.3
Commitment to purchase	$ 31.6
Pending litigation expense		3.0
Vehicles And Equipment [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Capital lease term	3 years
Vehicles And Equipment [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Capital lease term	6 years
Building and improvements [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Remaining term on capital lease	4 years
Operating lease term	1 year
Building and improvements [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Remaining term on capital lease	5 years
Operating lease term	5 years
Property And Equipment [Member]
Loss Contingencies [Line Items]
Capital lease carrying value	$ 17.2	25.2
Capital leases, accumulated depreciation	$ 42.5	37.1
Selling, general and administrative expenses [Member]
Loss Contingencies [Line Items]
Pending litigation expense		$ 3.0