Note D - Marketable Securities and Time Deposits - Marketable Securities and Time Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Short-term Deposits [Member]
Marketable debt securities, amortized cost	$ 5,707	$ 5,568
Marketable securities and time deposits, unrealized gains (losses), net
Marketable debt securities, estimated fair value	5,707	5,568
US Government-sponsored Enterprises Debt Securities [Member]
Marketable debt securities, amortized cost	24,305	23,645
Marketable securities and time deposits, unrealized gains (losses), net	(45)	(114)
Marketable debt securities, estimated fair value	24,260	23,531
Corporate Debt Securities [Member]
Marketable debt securities, amortized cost	76,698	79,072
Marketable securities and time deposits, unrealized gains (losses), net	(83)	(387)
Marketable debt securities, estimated fair value	76,615	78,685
Marketable debt securities, amortized cost	106,710	108,285
Marketable securities and time deposits, unrealized gains (losses), net	(128)	(501)
Marketable debt securities, estimated fair value	$ 106,582	$ 107,784