Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Years	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Operating Leases, Rent Expense	$ 10.7	$ 9.6	$ 10.1
Letters of Credit Outstanding, Amount	$ 6.3
Long-term Purchase Commitments, Range of Years, Minimum | Years	1
Long-Term Purchase Commitments, Range of Years, Maximum | Years	3
Long-term Purchase Commitment, Amount	$ 205.0	191.0
Asset Retirement Obligation [Abstract]
Balance, beginning of period	1.8	4.8
Liabilities Incurred	0.4	0.0
Liabilities settled	0.0	(2.0)
Revisions to estimated cash flow	0.0	(1.1)
Accretion expense	0.1	0.1
Balance, end of period	2.3	1.8	$ 4.8
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	7.0
2019	6.0
2020	4.7
2021	2.8
2022	2.6
Thereafter	18.3
Total	41.4
Retail Store [Member]
Operating Leases, Rent Expense	$ 0.6	$ 0.6