Note G - Treasury Stock (Details Textual) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2019	Apr. 30, 2017
Treasury Stock, Value, Acquired, Cost Method	$ 1,472,000	$ (0)	$ 321,000	$ 174,000	$ 11,823,000	$ 1,618,000
Treasury Stock, Shares, Ending Balance (in shares)	5,957,018						5,957,018	5,907,263
Treasury Stock, Value, Ending Balance	$ 158,630,000						$ 158,630,000	$ 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)							49,755
Treasury Stock, Value, Acquired, Cost Method							$ 1,793,134