Notes Payable and Accrued Interest (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Notes payable and accrued interest [Abstract]
Credit Facility principal	$ 67,800,000	$ 65,200,000
Credit Facility accrued interest	65,700	472,700
Notes payable and accrued interest	67,865,700	65,672,700
Credit Facility [Abstract]
Credit facility, borrowing capacity replaced	90,000,000
Credit facility maximum borrowing capacity	130,000,000
Warrant [Member]
Class of Warrant or Right [Line Items]
Maximum number of shares called through warrant (in shares)	81,224
Exercise price of warrants (in dollars per share)	$ 8.75
Credit Facility [Member]
Credit Facility [Abstract]
Expiration date	Sep. 30, 2015
Unused amount of the credit facility	22,200,000	24,800,000
Available borrowing capacity	$ 1,100,000	$ 17,400,000
Weighted average interest rate on credit facility (in hundredths)	4.00%	4.17%