Note 7 - Share Repurchase Program (Details Textual) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2015	Dec. 31, 2007
Stock Repurchase Program, Number of Shares Authorized to be Repurchased					2,000,000	1,000,000
Stock Repurchase Program, Authorized Amount					$ 40,000
Stock Repurchased and Retired During Period, Shares	455,581	941,024
Stock Repurchased and Retired During Period, Value	$ 7,500	$ 16,200	$ 7,513	$ 16,175