Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Allowance for receivables	$ 516,000	$ 490,000
Accumulated depreciation and depletion	$ 184,129,259	$ 183,868,729
Capital stock, par value	$ 2.5	$ 2.5
Capital stock, shares authorized	10,000,000	10,000,000
Capital stock, shares issued	2,600,232	2,599,532
Capital stock, shares outstanding	2,600,232	2,599,532
Class B Capital Stock [Member]
Capital stock, par value	$ 2.50	$ 2.5
Capital stock, shares authorized	10,000,000	10,000,000
Capital stock, shares issued	1,366,699	1,367,399
Capital stock, shares outstanding	1,366,699	1,367,399