Notes Payable and Accrued Interest (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Notes payable and accrued interest [Abstract]
Notes payable and accrued interest	$ 77,527,300	$ 67,865,700
Credit Facility [Abstract]
Borrowings under Credit Facility	19,000,000	19,900,000
Repayments of Credit Facility	9,300,000	17,300,000
Credit Facility [Member]
Notes payable and accrued interest [Abstract]
Credit Facility principal	77,500,000	67,800,000
Credit Facility accrued interest	27,300	65,700
Notes payable and accrued interest	77,527,300	67,865,700
Credit Facility [Abstract]
Credit facility, borrowing capacity replaced	90,000,000
Credit facility maximum borrowing capacity	130,000,000
Borrowings under Credit Facility	19,000,000	19,900,000
Repayments of Credit Facility	9,300,000	17,300,000
Expiration date	Sep. 30, 2015
Unused amount of the credit facility	52,500,000	22,200,000
Available borrowing capacity	$ 0	$ 1,100,000
Weighted average interest rate on credit facility (in hundredths)	3.94%	4.00%