Concentration of Credit Risk (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Concentration Risk [Line Items]
Number of significant customers	4	3
Payments received from customers	$ 180,000	$ 130,400
Accounts receivable, allowance for doubtful accounts	2,419,400	1,924,400
Operating leases, minimum future lease revenue payments receivable under noncancelable leases [Abstract]
2013	16,916,900
2014	10,941,200
2015	6,747,000
2016	5,389,200
2017 and thereafter	2,728,300
Total	42,722,600
Finance leases, minimum future lease revenue payments receivable under noncancelable leases [Abstract]
2013	296,700
2014	84,000
2015	84,000
2016	84,000
2017	73,500
Total	622,200
Interest income included finance lease	211,700
Customer One [Member]
Concentration Risk [Line Items]
Receivables	3,300,000
Accounts receivable, allowance for doubtful accounts	2,419,400
Customer One [Member] | Lease Revenue [Member]
Concentration Risk [Line Items]
Lease revenues and receivables from significant customers (in hundredths)	15.00%	19.00%
Customer One [Member] | Receivable [Member]
Concentration Risk [Line Items]
Lease revenues and receivables from significant customers (in hundredths)	71.00%	76.00%
Customer Two [Member]
Concentration Risk [Line Items]
Receivables		$ 2,246,800
Customer Two [Member] | Lease Revenue [Member]
Concentration Risk [Line Items]
Lease revenues and receivables from significant customers (in hundredths)	13.00%	14.00%
Customer Three [Member] | Lease Revenue [Member]
Concentration Risk [Line Items]
Lease revenues and receivables from significant customers (in hundredths)	11.00%	13.00%
Customer Four [Member] | Lease Revenue [Member]
Concentration Risk [Line Items]
Lease revenues and receivables from significant customers (in hundredths)	10.00%