Goodwill and Other Intangible Assets - Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 40.6				$ 36.2				$ 40.6	$ 36.2
Accumulated Amortization	(18.0)				(15.4)				(18.0)	(15.4)
Net Carrying Amount	22.6				20.8				22.6	20.8
Amortization of intangible assets	0.6	0.7	0.7	0.6	0.7	0.6	0.7	0.7	2.6	2.7	3.0
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	2.8								2.8
2016	2.7								2.7
2017	2.5								2.5
2018	2.3								2.3
2019	2.3								2.3
Customer relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	21.1				21.1				21.1	21.1
Accumulated Amortization	(5.6)				(4.1)				(5.6)	(4.1)
Net Carrying Amount	15.5				17.0				15.5	17.0
Non-competiiton agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3.2				3.2				3.2	3.2
Accumulated Amortization	(2.4)				(1.8)				(2.4)	(1.8)
Net Carrying Amount	0.8				1.4				0.8	1.4
Internally developed and other purchased software [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	16.3				11.9				16.3	11.9
Accumulated Amortization	(10.0)				(9.5)				(10.0)	(9.5)
Net Carrying Amount	$ 6.3				$ 2.4				$ 6.3	$ 2.4