Notes Payable and Long-Term Debt (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 19, 2009	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Sep. 30, 2012	Jan. 31, 2012	May 26, 2010	Jun. 30, 2013 Promissory Notes [Member]	Dec. 31, 2012 Promissory Notes [Member]	Jul. 31, 2012 Promissory Notes [Member]	Dec. 31, 2012 Line of Credit [Member]	Dec. 31, 2009 Interest Rate Swap [Member]	Dec. 31, 2010 Cash Flow Hedging [Member]
Debt Instrument [Line Items]
Notional amount of interest rate	$ 3,000,000								$ 9,000,000
Description of variable rate basis	three-month LIBOR
Long-term debt, basis spread on variable rate	3.40%
Interest rate, stated percentage	7.02%											1.00%	4.50%
Derivative, fixed interest rate									8.49%
Cash flow hedge, liability at fair value														317,000	667,000
Cash flow hedge, derivative instrument liabilities at fair value		984,000		984,000		1,521,000
Unrealized gain on interest rate swap		(302,000)	244,000	(354,000)	159,000	214,000
Available-for-sale securities pledged as collateral		1,474,000		1,474,000		1,557,000
Line of credit facility, maximum borrowing capacity							4,000,000	700,000				13,000,000
Line of credit facility, interest rate								5.00%
Drawns on line of credit		200,000		200,000		125,000
Long-term debt, interest rate at period end										4.25%	4.25%		4.50%
Amount outstanding										10,500,000	10,500,000
Annual installments		$ 1,167,000		$ 1,167,000