Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Allowance for credit losses and recorded investment in financing receivables
Balance January 1	$ 2,572	$ 2,257
Provision for credit losses	4,142	263
Recoveries	3	52
Write-offs	(2,144)
Balance December 31	4,573	2,572
Finance Leases [Member]
Allowance for credit losses and recorded investment in financing receivables
Balance January 1	525	210
Provision for credit losses	8	263
Recoveries	3	52
Write-offs	(97)
Balance December 31	439	525
Notes Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
Balance January 1	2,047	2,047
Provision for credit losses	4,134	0
Recoveries	0	0
Write-offs	(2,047)
Balance December 31	$ 4,134	$ 2,047