Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Allowance for receivables	$ 737,000	$ 670,000
Accumulated depreciation and depletion	$ 190,551,539	$ 182,427,598
Capital stock, par value	$ 2.5	$ 2.5
Capital stock, shares authorized	10,000,000	10,000,000
Capital stock, shares issued	2,583,709	2,569,831
Capital stock, shares outstanding	2,583,709	2,569,831
Class B Capital Stock [Member]
Capital stock, par value	$ 2.5	$ 2.5
Capital stock, shares authorized	10,000,000	10,000,000
Capital stock, shares issued	1,429,925	1,443,803
Capital stock, shares outstanding	1,429,925	1,443,803