Notes Payable and Accrued Interest (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Notes payable and accrued interest [Abstract]
Credit Facility principal	$ 67,500,000	$ 67,800,000
Credit Facility accrued interest	65,300	65,700
Notes payable and accrued interest	67,565,300	67,865,700
Credit Facility [Abstract]
Credit facility, borrowing capacity replaced	90,000,000
Credit facility maximum borrowing capacity	130,000,000
Credit Facility [Member]
Credit Facility [Abstract]
Expiration date	Sep. 30, 2015
Unused amount of the credit facility	62,500,000	22,200,000
Available borrowing capacity	$ 12,916,000	$ 1,113,500
Weighted average interest rate on credit facility (in hundredths)	4.00%	4.00%