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Balance Sheets (Parentheticals) (USD $)
Dec. 31, 2011
Dec. 31, 2010
Treasury stock, shares 4,299,434 4,166,034
Nonvoting Common Stock
    
Common stock, par value (in dollars per share) 1 1
Common stock, shares authorized 50,000 50,000
Common stock, shares issued      
Voting Common Stock
    
Common stock, par value (in dollars per share) 1 1
Common stock, shares authorized 40,000,000 40,000,000
Common stock, shares issued 23,382,566 23,003,285
Common stock, shares outstanding 19,083,132 18,837,251