Commitments and Contingencies Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Future minimum rentals under noncancelable subleases	$ 0.1
Operating leases, rent expense	29.3	$ 8.1	$ 4.2
Commitment to purchase	$ 4.8
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]
Loss Contingencies [Line Items]
Remaining term on capital lease	7 years
Building and improvements [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Operating lease term	1 year
Building and improvements [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Operating lease term	5 years
Property And Equipment [Member]
Loss Contingencies [Line Items]
Capital lease carrying value	$ 32.6	26.3
Capital leases, accumulated depreciation	$ 28.8	$ 21.5