Note K - Outstanding Stock Option Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Stock Option [Member]
Outstanding, Shares (in shares)	766,924	694,552	638,800
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 28.20	$ 24.34	$ 22.21
Exercised, Shares (in shares)	(43,919)	(85,063)	(159,309)
Exercised, Weighted Average Exercise Price (in dollars per share)	$ 21.23	$ 21.53	$ 19.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		166,861	218,707
Granted, Weighted Average Exercise Price (in dollars per share)		$ 40.68	$ 27.03
Forfeited/Expired, Shares (in shares)		(9,426)	(3,646)
Forfeited/Expired, Weighted Average Exercise Price (in dollars per share)		$ 25.53	$ 24.84
Outstanding, Shares (in shares)	723,005	766,924	694,552
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 28.62	$ 28.20	$ 24.34
Exercised, Shares (in shares)	(43,919)	(85,063)	(159,309)
Outstanding, Intrinsic Value	$ 5,872
Vested plus expected to vest at December 31, 2015 (in shares)	664,824
Vested plus expected to vest, Weighted Average Exercise Price (in dollars per share)	$ 28.35
Vested plus expected to vest, Intrinsic Value	$ 5,530
Exercisable at December 31, 2015 (in shares)	540,287
Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 26.35
Exercisable, Intrinsic Value	$ 5,263
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0
Vested plus expected to vest at December 31, 2015 (in shares)	512,897