Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Allowance for credit losses and recorded investment in financing receivables
Beginning balance	$ 4.4	$ 4.6
Provision for credit losses	0.1
Write-offs	(0.1)	(0.2)
Ending balance	4.4	4.4
Finance Leases [Member]
Allowance for credit losses and recorded investment in financing receivables
Beginning balance	0.3	0.5
Provision for credit losses	0.1
Write-offs	(0.1)	(0.2)
Ending balance	0.3	0.3
Notes Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
Beginning balance	4.1	4.1
Provision for credit losses	0.0
Write-offs	0.0	0.0
Ending balance	$ 4.1	$ 4.1