Note F - Treasury Stock (Details Textual) - USD ($)				9 Months Ended
	Apr. 05, 2016	Mar. 18, 2016	Feb. 18, 2016	Sep. 30, 2016	Dec. 31, 2015	May 31, 2014
September 2011 Reauthorization [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased						500,000
Treasury Stock, Shares, Acquired				149,687
Treasury Stock, Value, Acquired, Cost Method				$ 2,994,000
The 2016 Tender Offer [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		425,000	325,000
Treasury Stock Acquired Cost Per Share		$ 34	$ 30
Oversubscribed Shares Tendered [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	142,413
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	567,413
Treasury Stock, Value, Acquired, Cost Method	$ 17,600,000			$ 20,726,000
Treasury Stock Acquired Cost Per Share	$ 31
Treasury Stock, Shares				5,097,910	4,380,810
Treasury Stock, Value				$ 122,505,000	$ 101,779,000