Note G - Treasury Stock (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Apr. 30, 2017
Treasury Stock, Value, Acquired, Cost Method	$ 321,000	$ 1,618,000
Treasury Stock, Shares, Ending Balance (in shares)	5,916,438		5,907,263
Treasury Stock, Value, Ending Balance	$ 157,158,000		$ 156,837,000
September 2011 Reauthorization [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased (in shares)				500,000
Treasury Stock, Shares, Acquired (in shares)	9,175
Treasury Stock, Value, Acquired, Cost Method	$ 321,000