Note G - Treasury Stock (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Apr. 30, 2017
Treasury Stock, Value, Acquired, Cost Method	$ 36,000
Treasury Stock, Shares, Ending Balance	5,369,235	5,368,235
Treasury Stock, Value, Ending Balance	$ 129,219,000	$ 129,183,000
September 2011 Reauthorization [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			500,000
Treasury Stock, Shares, Acquired	1,000
Treasury Stock, Value, Acquired, Cost Method	$ 36,000