Accounts and Notes Receivable and Credit Quality of Notes Receivable (Allowance for Doubtful Accounts Receivable) (Details) (Notes receivable, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Notes receivable
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 5.9	$ 5.6
Charge-offs	(0.1)	0
Recoveries	0	0
Provision	2.4	1.0
Ending balance	8.2	6.6
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment [Roll Forward]
Beginning balance	5.9	5.6
Charge-offs	(0.1)	0
Recoveries	0	0
Provision	1.8	0.9
Ending balance	7.6	6.5
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment [Roll Forward]
Beginning balance	0	0
Charge-offs	0	0
Recoveries	0	0
Provision	0.6	0.1
Ending balance	$ 0.6	$ 0.1