Note 7 - Stock-Based Compensation (Detail) - Employee Stock Purchase Plan Activity (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shares purchased on the open market	108,132	65,843	60,017
Average per-share purchase price (in Dollars per share)	$ 38.96	$ 40.55	$ 37.07
Total purchase price discount (in Dollars)	$ 618,278	$ 401,346	$ 333,639