Note 4 - Share-Based Compensation (Detail) - Stock Option Activity (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Outstanding at December 31, 2012		455,918
Outstanding at December 31, 2012 (in Dollars per share)		$ 30.34
Granted	29,448	31,630
Granted (in Dollars per share)	$ 52.42
Exercised	(39,751)
Exercised (in Dollars per share)	$ 13.21
Outstanding at March 31, 2013	445,615
Outstanding at March 31, 2013 (in Dollars per share)	$ 33.33
Outstanding at March 31, 2013	6 years 310 days
Outstanding at March 31, 2013 (in Dollars)	$ 10,909
Exercisable at March 31, 2013	195,325
Exercisable at March 31, 2013 (in Dollars per share)	$ 26.74
Exercisable at March 31, 2013	5 years 102 days
Exercisable at March 31, 2013 (in Dollars)	$ 6,068