NOTES PAYABLE (Additional Information for Notes Payable) (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Restricted cash	$ 145,413,726	$ 118,130,253
Short-term Debt [Member]
Short-term Debt [Line Items]
Maximum balance outstanding during the year	309,304,826	204,880,916
Interest expense	$ 4,701,767	$ 3,342,011
Weighted average interest rate	0.69%	1.29%
Short-term Debt [Member] \| Minimum [Member]
Short-term Debt [Line Items]
Finance charge per contract	0.05%	0.05%
Percentage of restricted cash backing notes payable	10.00%
Short-term Debt [Member] \| Maximum [Member]
Short-term Debt [Line Items]
Finance charge per contract	0.15%	0.50%
Percentage of restricted cash backing notes payable	100.00%

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

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