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