Net Investment in Sales-Type Leases allowance credit loss rollforward (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Net Investment in Sales-Type Leases [Abstract]
Allowance for Notes, Loans and Financing Receivable, Current	$ 100,000		$ 100,000		$ 500,000
Allowance for Notes, Loans and Financing Receivable, Noncurrent	100,000		100,000		100,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning of period	190,000	257,000	607,000	284,000
Current period provision (reversal)	6,000	422,000	19,000	422,000
Direct write-downs charged against the allowance	0	0	(413,000)	0
Recoveries of amounts previously charged off	(12,000)	(20,000)	(29,000)	(47,000)
Allowance for credit losses, end of period	$ 184,000	$ 659,000	$ 184,000	$ 659,000