Notes Payable and Accrued Interest (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Notes Payable and Accrued Interest [Abstract]
Notes payable and accrued interest	$ 64,532,400		$ 67,865,700
Credit Facility [Member]
Notes Payable and Accrued Interest [Abstract]
Credit Facility principal	64,500,000		67,800,000
Credit Facility accrued interest	32,400		65,700
Notes payable and accrued interest	64,532,400		67,865,700
Credit Facility [Abstract]
Credit facility, borrowing capacity replaced		90,000,000
Credit facility maximum borrowing capacity		130,000,000
Expiration date	Sep. 30, 2015
Unused amount of the credit facility	65,500,000		22,200,000
Available borrowing capacity	$ 16,517,500		$ 1,113,500
Weighted average interest rate on credit facility (in hundredths)	3.94%		4.00%