Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013
Allowance for credit losses and recorded investment in financing receivables
January Balance	$ 4.5	$ 4.5	$ 4.5
Provision for credit losses	0.5
March Balance	5.0	4.5	4.5
Finance Leases Financing Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
January Balance	0.4	0.4	0.4
Provision for credit losses	0.5
March Balance	0.9	0.4	0.4
Notes Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
January Balance	4.1	4.1	4.1
Provision for credit losses	0
March Balance	$ 4.1	$ 4.1	$ 4.1